The only product I have seen so far that does a good job of supporting multiple screens (also known as a virtual desktop) would be DameWare. It allows you to select individual monitors or do a "virtual desktop" which shrinks both monitors to fit onto your screen.
I use it all the time here. They have a trial version at their website:
http://www.dameware.com
The product you are looking for is the "Mini Remote Control"