I have one. It's called Remote Mouse. And it's the coolest thing ever.
So here's what it does. It turns your iPhone into a mouse/keypad for your PC.
Now the reason I think this is so cool, I have a HTPC set up, but no remote.
Wireless mice and keyboards are bulky to use and don't have the greatest range.
The Remote Mouse on the iPhone will work anywhere it gets a wifi signal.
It's free, it's easy to set up and it works great. I'm typing on it now.
All you have to do is install the app from iTunes onto your iPhone and a small receiver app onto your PC.
When you run the app on your PC it gives you an IP address, enter that into the app on the iPhone and it's ready to go.
Get the app for your PC/Mac here: http://www.remotemouse.net/
And the app for your iPhone/iPod: http://itunes.apple.com/app/id385894596?mt=8
Or iPad: http://itunes.apple.com/app/id431038047?mt=8