Still in the early stage but looks like a useful tool. Basically a constantly updated catalogue is being built of .exe files (I have suggested DLLs be added too) and each safe file is being "check-summed". This little utility scans your system for exe files and compares the checksums to ensure you have a pukka copy.
The database is already substantial but needs to grow (and be extended in scope) to be really useful but it looks like a really good start.
Note there appears to be a slight scripting bug in the initial release (just a script error when displaying the user interface) but it is being addressed and doesn't affect the functionality of the program.
Check here for details.