Track Car iphone apps

[T89 Callan]

What are the best app's for the iPhone to add to the track day experince?

I have the new 3G S and I'm already using a Free Speedo app instead of the broken speedo in the car and have some Dyno+ app which seems pretty crap.

Can anyone recomend anything fun/useful/good that they have used in trak cars?

Also can anyone recomend a decent decible meter? The free one I downloaded only goes upto 100dB.

[Pommygranite]

Dynolicious is ok.