I just downloaded this app.  I want to see how good or not as good I am with live tempo.  This program tracks tempo over a period of time.  It also lets you play music from your iPhone and will track tempo of what is playing or what it hears live.  Pretty incredible.
$2.95.  
 
http://www.youtube.com/watch?v=88ivh3Sd3kg
 
I think this an awesome tool for drummers.
 
Rimshot
 

Sounds pretty cool. I'm using a Korg hardware unit that I tap a tempo from a song into. The app seems like an easier solution.

Hey Starise, 
 
The app I speak of records the tempo throughout the song so you can see how well you did.  Yes it will find the tempo for you but in my case, I want to see the complete tempo map for a song.  This is the only app I have seen that does this so effortlessly and on my iPhone!