Case Study
HK Relay SMS Gateway
Android app that turns any phone into an SMS gateway with REST API and webhook support.
DIRECT
for Personal ProductJan 2026android
kotlin
sms gateway
rest api
HK Relay solves a simple problem - sending SMS from web applications without expensive SMS gateways. Just use an old Android phone.
API & Integration
The app exposes a REST API for sending messages and supports webhooks for delivery reports and incoming messages. Built with Kotlin and Ktor for the embedded HTTP server.
Reliability
Includes queue management for handling high volumes and retry logic for failed messages.