Notification App for Deaf and Hearing Impaired

Sensa App


The app is built for our client in Netherland. He approached us with the idea of creating a notification app for deaf and hearing impaired. The app works together with Sensa RF gateway (use of Internet of things technology). The gateway receives signals from doorbells, smoke detectors, telephone ring, fire alarm, baby monitor, etc. and passes them to the app, thereby alerting deaf and hearing impaired. The App will alert the user visually, it vibrates according to a unique pattern, plays a sound and it flashes.

Goal / purpose

The idea behind this app is to help the deaf and hearing
impaired with their day-to-day activities.

Technology / platform

  • iOS
  • Internet of things
  • X-code
  • Objective C


The app is for special users who are deaf and hearing imparied, so finding out a suitable way to send alert for events was a real challenge, as most of the alert notifications require hearing ability. So the notification has to be in the form of standard icons / images, with vibration and LED flash. Another challenge was to register for specific Ipv4 multicast group so that the app can send notification even if there is no internet connection or the app is running in bacground. The challenge was to keep application sockets active to receive signals from local network.

The solution

  • To confront the challenge of notification we decided to send alert notification via:
  • Corresponding standard icon/image
  • Vibrating phone device in specific pattern
  • Flash LED light of phone device in specific patter We defined a specific patter for each type of alarm/signal, for e.g. For Personal Call we defined “V.4 P.8 V.4 P.8” which means play vibration/LED flash for .4 seconds and pause for .8 seconds till targeted N seconds. Similarly we implemented this vibration pattern for all types of alarms/alerts. We also handled it in case of multiple alarms/alerts along with priority.To overcome the challenge of receiving notification even when the app is in background mode we kept application sockets active by configuring UI BackgroundModes as “audio” & “fetch” and using them:
  • By playing specific music file for each type of alarm/signal received from broadcast gateway.
  • If no alarm/signal then we are playing an empty audio file to keep the socket open/alive for longer time if application is in background or suspended.
  • By refreshing the app content in background using background fetch method provided by iOS SDK.


  • Help users (Specially deaf and hearing impaired) by notifying them for the day-to-day activities that require hearing abilities like doorbell, baby monitor, phone call, fire alarm etc.
  • Minimal configuration/setup with proper instructions to configure multicast Gateway (RFGateway).
  • Showing alarms/alerts received from Gateway (RFGateway) using standard icons/graphics to make it attractive and interactive.
  • The app is also able to receive and handle multiple alarms/alerts simultaneously.
  • In case of multiple alarms/alerts priorates notifications icons, vibration, LED flash and give equal time to each of them to notify the user.
  • Showing recent alarms/alerts history received from Gateway (RFGateway) to notify the user in-case missed the notification.