You're waiting in line for a coffee, eyeing a pastry, and your wrist-watch buzzes with a warning.

Flashing on the tiny screen of your Apple Watch is a message from an app called Lark, suggesting that you lay off the carbs for today. Speak into the Apple Watch's built-in mic about your food, sleep and exercise, and the app will send helpful tips back to you.

The notion of receiving nutrition advice from artificial intelligence on your wrist may seem like science fiction. But health developers like Lark are making a bet that Apple's first wearable device, the Apple Watch, will fly off the shelves and this kind of behavior will become the norm.

A typical interaction with a Lark weight loss coach (Lark)

Lark is just one of over a dozen health developers with new apps for the Apple Watch, which are focused on improving people's health and fitness. Some of these apps are essentially a smaller version of an existing iPhone app; others take advantage of the unique capabilities of the Apple Watch.

Apple has made no secret of its interest in medicine, and has recruited industry experts to work on services like ResearchKit and HealthKit, which aim to open up the flow of health data between consumers, mobile developers and medical researchers.

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But as it dabbles in health care, a notoriously regulated and privacy-conscious sector, Apple has also made steps to put you in control of how your data is shared.

Here's how it works for the Apple Watch: You can choose to share health information with third-party apps like Lark, including the amount of steps you've walked, via Apple's Health app, which comes with the device. Your health data, collected via the Apple Watch or the iPhone, is stored on Apple's HealthKit.

In advance of the Apple Watch's April 24th ship-date (although recent reports suggest there will be delays before the watch reaches your local Apple Store), KQED spoke with mobile developers from startups and big brands. Their offerings for the Apple Watch range from medication management apps to a button that provides instant, virtual access to a doctor.

"We haven't had a developer ecosystem for a product like a smartwatch," said Ben Bajarin, who specializes in consumer technology for Creative Strategies, a consulting firm. Similarly to the iPhone, the Apple Watch has its own App Store, which goes live on Thursday.

"This is unchartered territory."

A Message on the Wrist

Health app developers hope the Apple Watch will improve how doctors and patients communicate, particularly when it comes to sending urgent notifications and alerts.

Imagine a doctor receiving a buzz on the wrist for an e-prescription request, which could be approved with a few taps. A patient could receive a similar alert when test results are available, and caregivers might receive a flashing message on their Apple Watch when an elderly patient has taken a bad fall and needs assistance.

Developers are exploring all these possibilities and more.

[Scroll down to the graphic at the bottom for a more extensive list of apps. Or click the link here.]

Those of us with a smartphone have grown accustomed to receiving notifications from apps, such as an email from a medical clinic, which often goes unchecked. But with the watch, the notification is seen, heard, and most importantly, felt on the body.

"We are predisposed to small changes on the skin. It was not that long ago -- and is still the case in parts of the world -- that mosquitoes used to kill us with a light touch," said Ron Gutman, chief executive of HealthTap, a website and mobile app for secure video calls with a doctor.

"It is so easy to turn off a notification from a website, but you can't ignore what's on your wrist," he said.

Gutman was so intrigued by Apple's smartwatch that he developed three apps: One to help you manage you meds with notification reminders; another that connects you to a primary care doctor with the touch of a button; and a third, which helps physicians reach new patients.

Electronic health record company Drchrono developed two apps for the Watch. Both these apps (one is targeted to the patient; the other for the physician) are intended to help people manage chronic medical conditions, including diabetes and heart disease.

"Sometimes having alerts on your wrist is critical," said Daniel Kivatinos, cofounder of Drchrono.

"We've all had the experience of going to a hospital or doctor's office, and having no idea that they messaged me blood test results four or five months ago," he said.

Managing Medications

Gutman isn't the only developer delivering notifications to the wrist, with the hopes of changing people's behavior.

One popular category of the early Apple Watch apps is medication management. For people who are juggling a variety of medications -- all with different dose requirements -- an app that sends alerts to the wrist could prove useful.

WebMD, the company used by millions of people to check their medical symptoms, tossed around a bunch of ideas before settling on medication adherence.

"Of all the options we looked at, medication reminders was the crown jewel," said Ben Greenberg, who heads up mobile products at WebMD. Greenberg said the ideal interaction between the app and the user should be 10 seconds or less.

"All we wanted is for the user to be reminded that it's time to take their medication, and then quickly tell us whether they plan to take it or skip it or snooze. That interaction demands so little," he said. The app also instructs people whether to take their medication with food, or at a certain time of day.

Other companies that are developing medication adherence apps for the Apple Watch include MangoHealth, which can also tell you how well you've managed your prescriptions over time, and pharmacy giant Walgreens.

Appealing to Doctors

Some developers hope the Apple Watch will appeal to doctors to help them manage an overload of information.

Analyst Ben Bajarin received early access to the Apple Watch, which he uses during exercize — Analyst Ben Bajarin received early access to the Apple Watch, which he uses during exercise

Kivatinos, a developer and cofounder of Drchrono, is convinced that digitally-savvy doctors will flock to buy an Apple Watch, particularly those who work in small medical practices.

"Doctors are finally getting amazing hardware that just works, and they're willing to pay a premium for it," he said. Using DrChrono's app for the watch, a doctor can receive alerts, such as when a patient has arrived at their office.

The watch could prove useful in helping doctors communicate with each other about tricky medical cases, as well as with their patients. Doximity, the Facebook for doctors, has developed an app that care providers can use to dictate notes, send messages, and receive notifications that a fax has arrived.

However, the Apple Watch's appeal may be limited to certain specialties, such as family physicians and dermatologists.

Unlike Google Glass, the futuristic eyewear which has found some success in operating theaters, many surgeons routinely remove their rings and watches before procedures, to ensure their hands stay sterile.

Opportunities and Challenges

Privacy experts and policymakers have long-been concerned about developers that collect and sell personal health information.

Apple has responded to some of these fears by stressing its commitment to privacy, and barring third-party developers from selling health data to advertisers that it collects via Apple devices, like the iPhone and Apple Watch. After some high-profile hacks to celebrities' accounts, Apple forbade developers from storing sensitive health information in iCloud.

"Apple has clear privacy rules, but consumers should still be on guard," said Morgan Reed, executive director at The App Association, a Washington, D.C. nonprofit that works with patient advocates and app developers.

"Be prepared to take charge of your health information, and feel free to say no to sharing data with apps," said Reed.

In the future, there may be new privacy questions and concerns. Health experts and analysts expect to see far more sophisticated health-tracking in the Apple Watch, including a sweat sensor. At that point, the Watch may function as a regulated medical device of sorts, rather than a glorified fitness tracker.

Many health developers hope the watch will prove to be a tool for behavior change, as well as a new communications tool for doctors and patients alike.

"What we do know is that the general tracking of your steps and calorie intake isn't enough," said Bajarin, the analyst with Creative Strategies.

"How does this change people's behaviors and goal settings for the better? That’s the step that has been missing in the wearables trend. That’s where we need to go."

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