Feature Request: Monitor files or folders

I'dlike to be able to detect the presence or absence of a file, or the presence or absence of files in a folder. Case in point: i have an ubuntu server running uTorrent, which downloads files to a Temp folder and moves them out of the folder when completed. So I'd like powernap NOT to sleep the server while uTorrent is downloading, but to be able to sleep when uTorrent is not downloading anything. Note that process monitoring is not suitable, since uTorrent is constantly running, and that I/O or TCP monitor is also not suitable, since sometimes uTorrent just sits idle waiting for a suitable peer mid-download.

Thanks!