Over the last 15 years I've constantly found myself part of an on-call rotation where ever I have worked. It's par for the course as an Operations Engineer.
For many years I carried a Blackberry with me for two reasons:
* Mostly reliable message delivery
* Highly customizable notifications
Message delivery reliability has increased well across the board, so I don't feel that Blackberry has any special advantage here any more.
Customizable notifications was the real must-have feature. You could have SMS notifications repeat constantly until answered, or every minute or every few minutes. They could start out on vibrate, followed by quiet sounds, and then louder sounds.
It was, in a word, perfect.
With those days behind us, I've regularly looked for a modern system which could emulate the old Blackberry functionality. For the last year and a half I've been using Chomp SMS on Android because if has a crude repeat-notifications option. It kind-of sort-of works.
When Google Hangouts fully enabled support for Google Voice I wanted to switch to using that, but Hangouts has no repeat notification functionality, so if you miss a page, you're screwed.
Enter Repeating Notifications, a very cool app that lets you customize repeat notifications for *any* app.
It's also incredible simple to use: Install it, and in the settings enable repeat notifications for Google Hangouts. Then tap Google Hangouts, and choose the repeat interval. You can also choose how you want repeat notifications to be silenced: When you turn the screen on, when you unlock the phone, or when you open Google Hangouts.
I tried this with my last on-call rotation, with notification repeating set to 30 seconds. It worked like a charm.