Repeat Timer Pro. It lets me set 25 second timers every 25 minutes, for as many intervals as I want. I use it to encourage myself to rest my eyes and stretch my

Repeat Timer Pro. It lets me set 25 second timers every 25 minutes, for as many intervals as I want. I use it to encourage myself to rest my eyes and stretch my legs for 25 seconds every 25 minutes. It notifies me with just a little vibration. I think it cost $5, but there are probably free apps that do this too.