does a similar application to Timesnapper for Mac exist?
i think this should work http://timesheet-mac.en.softonic.com/mac
I've created a bash script which takes screen-shots every few seconds, combines them into an mp4 every hour, and combines the hourly mp4s into daily ones each day.
Uses ImageMagick to overly the current time on each screenshot, and ffmpeg to combine the screenshots into videos.
ManyTricks have recently released Time Sink. It sounds like it does some of what Timesnapper can. No screenshots though.
If you really want the actual screenshots you could try looking into scripting it using AppleScript and launchd. Shouldn't be that difficult to do.