First, yes you can check on the remote system and there are a few ways you can do that. One is SSH into the remote machine, run a perl one-liner (or remote script) on the remote box to report back the mtime (or checksum).

Getting a checksum would likely be quicker, but consider that you'll have to store the checksums somewhere then look them back up every program run for comparison, so that's likely to even things out.

EDIT: per Laurent_R, mtime will be faster in the long run. I was testing on a miniscule few-byte file.

-stevieb