The ABL engine has no built-in mechanism for that, and as Rob pointed out, you must define what exactly you mean by "no activity". The only way I know to achieve something like this is to use a third party OCX timer control that you reset whenever something happens in your application that you define as "activity" and trigger the "re-direct to login" when you receive the corresponding event from the OCX.
Heavy Regards, RealHeavyDude.