I’m about to tell you how a new way of designing apps changed my life. But to explain the power of this trend, I need to tell you about poop.

For the past five years or so, I’ve struggled with intestinal discomfort. I spent countless hours crawling the web searching for a possible diagnosis and tried dozens of different remedies and diets. Nothing seemed to help.

I decided I’d rather live with the problem (whatever it was) and hope for the best. Then, a chance encounter with a total stranger led me to start using a new kind of app that does things my doctor never could.

A while back, my friend Stephen and I chatted at the park while we watched our kids play. As Silicon Valley tech geeks do, we got to talking about apps. I mentioned Pana (which, full disclosure, I liked so much I invested in).

Here’s how it works: every time I need to do anything related to travel, I just ask Tim to handle it. Tim lives inside Pana; for all I know he may be a bot, artificial intelligence, or any number of people working behind the scenes under the persona of the fresh-faced Tim.

Tim functions something like a concierge. Instead of comparing comparing prices, flight times, connection difficulty, and frequent flyer point requirements, I just open the app and tell Tim what I need in plain English. Later I’ll receive some options for itineraries. Done!

As I described Pana to Stephen, a woman pushing her child on the swing next to us interjected, and asked exactly which app we were talking about. After I showed her Pana on my phone, she explained that her company did the exact same thing… but for health.

The woman was Stephanie Tilenius, CEO of Vida Health. As she walked us through her app, Stephanie mentioned that Vida is great for irritable bowel syndrome... if you happen to know anyone with that.

Did I ever!

Diagnosing a digestive problem is fiendishly difficult. It requires looking back through a detailed log to find what might be causing symptoms that don’t manifest until the food has time to work its way through the body a day or so later. Finding a solution involves not only understanding what I ate that might be causing the symptoms, but also what I did not eat that I should have. I had done this sort of detailed record keeping before on my own but it was incredibly time consuming and I always gave up after a few days.

I started using Vida. Over the next several weeks, I shared what I ate and how I was feeling with my coach Mindy who, like Tim from Pana, was a helpful face on the other side of the app. Like Pana, there was no complicated interface to learn. The app felt more like messaging with a friend than diagnosing a health problem.

Along with helpful suggestions, Mindy sent me regular reminders to send her snapshots of what I was eating. She also requested I text a number from 1 to 10 to quantify my symptoms — my “poo score,” we called it.

Soon, something interesting happened.

Mindy started analyzing my diet in ways neither my doctor nor I ever could. She looked at the nutritional content of what I was eating and searched for correlations with how I felt. Like a detective, she was on the hunt for the intestinal who-done-it. She started eliminating suspects from the food line-up and narrowing in on what might be triggering my symptoms by looking for clues in my diet. She told me what I should eat instead and, after changing my diet, I’m feeling better.

Mindy’s ability to diagnose the source of my problem was something my physician just didn’t have the time or ability to address. Without a way to carefully monitor and analyze what was going in and coming out of my body, how could he? Conversational apps like Vida, however, are designed to always be accessible, allowing users to send the kind of information a professional can use to provide more insights in less time.

This trend is bigger than travel and diet apps. The fact that these two very different services both use what I call an “assistant-as-app” to help users accomplish complex tasks, makes me think there’s more to this trend.

A version of this piece appeared on Nir Eyal’s blog, Nir and Far.