My son spends way too much time on games. I need parental control software that'll allow me to set per-day limits on a group of applications, or that will make application usage stats available in a processable format (such as CSV) either mailed to me or downloadable. I don't mind the application costing money; we're currently using qustodio, but that only allows per-app limits, not per-app-group limits, and it mails out tons of false positives on website usage (web monitoring is a plus but not a requirement).
Edit: this is for the Windows platform, and it would preferable impossible/non-trivial for him to turn this off. I don't need this to be hidden in any way -- he knows about it -- but I must accept that the temptation to play is too strong for him at this time.