IpBike app has programmable intervals with audio, voice and vibration prompts. Looks like beta ware but it's functional and free.
Cyclemeter is more sophisticated, has programmable timers for interval training, and the annual subscription is only $10. It uploads to Strava, no problems. But user data is accessible via the Cyclemeter app only as long as the annual subscription is paid. The free trial version is very limited so it's difficult to get a good sense of how much the app can do.
I used Cyclemeter for a couple of years, then let it lapse. I might renew in January just to have access to the programmable timers and other features. I haven't found another app quite like it. IpBike has some similar features and is free, but it looks and feels crude and unfinished. Starting some features in non-intuitive compared with Cyclemeter.