Sprint intervals - app?

[IsThatYouPaul]

Anyone know a good app (preferably free) to tell me when my little legs should go like the clappers?

I've just finished C25K in which Jo Whiley has successfully nudged me to run 5k in 33 mins.

I'd really like to get under 30 mins, and think I need to add sprinting things to do that. I found one with the right timer (jogrunsprint), but the robotic voice just says "run" "sprint" etc. I like a bit more ooomph!

Anyone found something that fits the bill?

[BrexitSucks]

DS has a British Army one.

[IsThatYouPaul]

Thanks Brexit I'll have a look.