This one is a kit you can build yourself for ~$30. It interfaces with your PC. The software is free.

I looked into that one already, and it's not $30.00. The $30.00 option is for only a subset of the entire parts list, as far as I can tell.

Still, even the complete kit is not a bad option at ~$50-$75, and I've messed with the software in "test" mode and it looks pretty cool.