You can use the SDK for learning the basic stuff.
When it comes to tuning user-inputs, memory use and performance
you should have a device available.

The iPad will take some time to reach a bigger market
share. But it can run iPhone apps from the start.

Some small recent games of mine:
Griefer 4k http://damocles11.byethost9.com/griefer4k.html
Kobold 4k http://damocles11.byethost9.com/kobold.html
Cave 4k http://damocles11.byethost9.com/cave4k.html