I came up with an idea tonight for a physical software mouse interaction that to my knowledge has never been used. I was wondering if anyone knows a way to search patents so I can find anything similarly patented.
This really isn't a DIY project, you should hire an experienced shark to do the work.
Still, look here and try to find classifications that fit your idea. That will make it easier to find relevant patents, which can be hard to track down since different aplicants use different terminology.