I'm not as familiar with the WP7 API as I should be but I've done some Zune XNA programming and you have access to the touchscreen and accelerometer fairly straightforwardly. I can safely assume a port between the two would be relatively painless.
You get a list of
TouchLocations from XInput and you can do what you will with them. Each touch has an ID that allows you to identify drags/swipes.
The Accelerometer just gives you a 3D vector showing the current acceleration (with 0,-1,0 being the norm due to gravity). This tutorial gives a good example of using the Zune's interface.