[nttdemented]

Haven't heard of anything like a mouse pad type control but most custom ROM's have smart touch enabled wich allows the ring around the dpad to be used a'la iPod to zoom in and out or scroll in most apps. Doesn't work everywhere though. Its called Smart Touch. Don't know if it can be enabled in a stock ROM but I think with some reg edits and a cab it should be possible. Search around for Smart Touch here and/or in XDA to see what turns up.