I need a Timer App that will sound when I'm on the phone

[Oatboy]

All of the Timers I've installed so far will not interrupt me when I'm on the phone. But that's exactly what I need my timer to do.

I've tried three different Apps: Kitchen Timer, Stopwatch and Timer, and Ultimate Stopwatch and Timer. No luck. No setting I can find to affect this.

I'm grateful for any tips.

Running Android 2.3.7 on a Motorola Defy Pro