Diamond Edge

Android and Kotlin Multiplatform apps, with the AI on the phone.

Diamond Edge designs, builds and ships mobile apps from one Kotlin and Compose Multiplatform codebase for Android and iOS. It's run by Reed Ellsworth, a principal engineer with 14 years of Android across consumer hardware, kiosks and TV.

About Reed Case study: speech recognition on the phone

Apps

Each one is Kotlin and Compose Multiplatform for Android and iOS, with the iOS release (signing, TestFlight, App Store review) handled in-house alongside Google Play.

Rimbalo

Professional dictation that runs in airplane mode. Speech recognition, voice activity detection and the decoder all run on the phone; the Android build has no network permission at all.

KMP · LiteRT · Parakeet-TDT · Silero VAD · Compose

How it works Product page

Diamond Tabletop

Eight card and board games, from Hearts to Gin Rummy, with bots for empty seats and real-time multiplayer across phones. Game rules ship as downloaded script bundles, not app code.

KMP · Compose · WebSockets · Ktor · Room

How it works App Store Google Play

Napkin Scores

A score pad for card nights, with ready-made scorecards for Flip 7, Qwirkle, Five Crowns, Skyjo and more. Nothing typed leaves the phone: no sign-in, no ads, no analytics.

KMP · Compose · Napkin theme library

How it works App Store Google Play

On-device AI

Models that run on the phone, chosen by measurement on real hardware: latency, memory, battery, heat, and whether the output is right.

Shipping in Rimbalo

Speech recognition on LiteRT

NVIDIA's Parakeet-TDT converted to LiteRT, running on the GPU or CPU of Android and iOS phones.

Read the case study

  • 20 s of speech decoded in under 0.4 s on the CPU of both reference phones, and in 0.10 s on an iPhone SE 3 GPU.
  • Found and fixed an fp16 overflow inside LayerNorm that made two different phone GPUs return the same wrong answer: output similarity went from −0.03 to 0.9997.
  • A Kotlin TDT decoder proven token-for-token against NeMo in CI, and a Kotlin port of NeMo's log-mel preprocessor.
  • Evaluated three on-device LLMs for writing summaries. The one chosen put a false statement in 22% of them, so the generative model came out.

Open source · KMP

AI Harness

An evaluation rig for on-device language models, on Android, iOS and desktop.

Read more · GitHub

  • Claude, Gemini and local GGUF models (llama.cpp through llamatik) behind one streaming interface.
  • A headless runner scores graded suites while recording time-to-first-token, battery, thermal status and peak memory per case.
  • Schema-constrained JSON decoding for the on-device models.

Open source · Python

llm-eval-ci

Graded YAML suites with a pass-rate gate, so a prompt or model change that regresses quality fails the build.

Read more · GitHub

  • An async runner with bounded concurrency and deterministic scorers.
  • Per-call cost and latency, and refusals reported as their own status.
  • The same run-record format the AI Harness writes from the phone.

Open source

Kotlin Multiplatform libraries on Maven Central and GitHub.

KmLogging

Logging for Kotlin Multiplatform on Android, iOS, JVM and JS, using each platform's own logger. Adopted by hundreds of companies. When logging is off, a call costs one boolean check: the API is inlined and lazy, and each class's tag is computed once.

com.diamondedge:logging · 136 ★

GitHub Maven Central

DiamondCharts

A two-series line chart drawn by DiamondCharts

The first charting library for Jetpack Compose: line, bar, stacked, area, pie, scatter and stock charts, now on Compose Multiplatform.

com.diamondedge:charts

GitHub Maven Central

Napkin

Buttons, checkboxes and a text field drawn as if sketched on a napkin

A Compose Multiplatform theme in which every component looks hand-drawn. Outlines come from a seeded sketcher, so they wobble but stay put between frames. It's the look of Napkin Scores.

Compose Multiplatform · Material 3

GitHub

Founder

Reed Ellsworth is a principal software engineer: 14 years of Android, and author of the libraries above.

Before Diamond Edge's current apps, Reed was the sole Android engineer on Weber's Summit Smart Valve grill, owning its UI from architecture to production, and built the companion app that 134,000 users rate 4.6 stars, with live temperature and cook state streamed over BLE and Wi-Fi through multi-hour cooks. Before that, Reed led Android for point-of-care kiosks on more than 100,000 devices at Outcome Health, and for Sling TV's live-streaming app with 1M monthly Android users, where a single APK came to serve phones, tablets and TVs.

Reed is looking for a full-time role in Android, Kotlin Multiplatform or on-device AI.

Contact on LinkedIn GitHub

Skills

Android and KMP
Kotlin, Jetpack Compose, Compose Multiplatform, Coroutines, Flow, Room, Koin, Hilt, Navigation 3, Material 3, Gradle, BLE, AOSP
On-device AI
LiteRT, llama.cpp, GGUF quantisation, model conversion, evaluation on real hardware, constrained decoding
Architecture
Unidirectional data flow, MVVM, repository pattern, dependency injection, modularisation
AI-assisted development
Claude daily, with prompt, context and harness engineering
  1. 2020 – nowDiamond Edge, founder. Rimbalo, Diamond Tabletop, Napkin Scores, AI Harness.
  2. 2021 – 2026Weber / Blackstone. Smart-grill UI and companion app; led the move to Compose, Coroutines and Flow.
  3. 2019 – 2021Outcome Health, Android lead. Kiosk fleet: provisioning, remote debugging, OTA updates.
  4. 2014 – 2019Sling TV, principal engineer. Live TV on Android phones, tablets, Fire TV and Android TV; full accessibility.
  5. 2005 – 2014FamilySearch. Desktop indexing client used by volunteers worldwide; first Android prototypes.
  6. 1997 – 2014Diamond Edge, first era. Developer tools used at thousands of companies: VB Converter, Diamond Grid, KScript.
  7. EducationMS Computer Science, University of Southern California. MS and BS Mechanical Engineering, Brigham Young University, with an emphasis on AI in design.