Leo / About the founder

I built Leo because I needed it.

I've worked both sides of the chart — as a 911 paramedic running 12-hour shifts and as a patient managing my own chronic conditions across notebooks, portals, and apps that didn't talk to each other. Leo is the app I needed in both rooms.

Mark Sheffield · founder & paramedic
01 · The story

Two rooms, same problem.

Chronic-illness data is fragmented by default. Some of it lives in a paper notebook. Some of it in a patient portal you have to log in to a hospital's 2008 website to read. Some in three apps that each track one thing and refuse to talk to each other. The patient is the integration layer — re-explaining a thirty-year medical history at every appointment, from memory.

On the trucks, patients arrived who couldn't name their own medications. They'd brought the pill bottles in a plastic bag, or a list scrawled on the back of a receipt. People who had been managing their own care for years.

That's the paramedic view. The patient view is the same thing from the inside — keeping notes in a journal, photos of pill bottles on your phone, screenshots of lab results, a calendar event you set to remember the dose. It works. Until you're tired, or sick, or in an ED with someone who needs the whole picture in thirty seconds.

I started building Leo because I wanted one calm place for the whole picture. Not a chatbot to decide things for you. Not an AI prediction that tells you when you're about to get sick. Just a record — meds, vitals, symptoms, journal entries, lab results — that you can actually use, and actually share with the people who care for you.

02 · The journey

By way of twelve, seventeen, and a thousand shifts.

Age 12
First lines of code

Started writing my first programs — the long road in.

Age 17
Earned my EMT

First time in the back of an ambulance with a card that said I belonged there.

2021
Started undergrad

Bachelor of Science in Emergency Medicine, eventually graduating Magna Cum Laude.

2021 – 2024
CPR Instructor

Three years teaching CPR — the foundation that everything else got built on.

2022 – 2024
Research at the school of medicine

Three studies, two published papers — sleep and teamwork in clinical environments.

2023
Medical Assistant

Clinic-side work between certifications. Different room, same patients.

2023 – 2024
Paramedic school

Full paramedic curriculum on top of undergrad. The accelerated lane.

2024 – 2025
911 medic on the trucks

12-hour shifts. Where the idea for Leo went from a notebook to a build.

2024 – 2025
Critical Care + Community Paramedicine training

Two specializations in progress — exams still ahead.

Now
Building Leo

The app I wanted in both rooms, written in Swift / SwiftUI for iPhone, watchOS, and the home-screen widgets that live on the lock screen.

03 · The credentials

Letters after the name, receipts on the wall.

NRP
Neonatal Resuscitation Program
ACLS
Advanced Cardiovascular Life Support
PALS
Pediatric Advanced Life Support
AMLS
Advanced Medical Life Support
EPC
Emergency Pediatric Care
GEMS
Geriatric Emergency Medical Services
PHTLS
Pre-Hospital Trauma Life Support
BLS / CPR
Instructor
Stop the Bleed
Instructor
And the longer line
Nationally Registered Paramedic. Bachelor of Science in Emergency Medicine, Magna Cum Laude. Multi-time Dean's List. Critical Care Paramedicine and Community Paramedicine training — exams still ahead. Co-author on two industry publications. The kind of resume that mostly shows up on a slide; what actually matters is the patients behind every certification on the list.
04 · The principles

Four rules, taped to the wall.

Built by a paramedic-patient.

I have chronic conditions of my own. I'm the first user, and Leo's design decisions get tested against my own data before they ship to anyone else's.

The decision: build for the room I'm actually sitting in.

No medical advice. Ever.

Leo doesn't interpret your data clinically. It doesn't tell you what's wrong. It doesn't prescribe, diagnose, or alert you that something is dangerous. That's not Leo's job — and it's not safe for it to pretend otherwise.

The decision: observe, never prescribe.

Your story is yours.

Your data lives in your encrypted Leo account. We don't sell it, we don't broker it, we don't train models on it. Sharing happens only when you grant a specific permission to a specific person — and you can revoke it any time.

The decision: the patient owns the record. Full stop.

Calm over noise.

No red shame icons for missed doses. No streaks to break. No panic-inducing notifications. The chronic-illness day is hard enough; Leo isn't here to gamify the hard parts.

The decision: every UI choice asked, would I want this on a bad day?
05 · The horizon

One calm place for the whole picture.

Over the next three years, Leo expands its condition catalog, deepens the on-device math, and adds hubs for the diseases that mainstream apps ignore. The shape stays the same — meds, vitals, sleep, mood, labs, journal, notes, side by side — clear enough that you'd hand it to a new doctor without a second thought.

If this resonates, you can see what Leo actually does, or join the beta.

Direct to founder · support@leomindbody.com