You don't. You track by task, not by time. You also assume that as professionals the remote employees are not taking the piss unless proven otherwise. This is where the task tracking comes in. As long as the engineers complete their assigned tasks on time, and to an agreed level, then it's irrelevant how many hours they worked. You've already budgeted and committed to paying them a working week, so if they manage to do their tasks in 4 days instead of 5, who cares?
If the engineer is failing to meet the task deadlines, THAT'S when you start asking for hours worked proof.
IT will never be considered a 'Professional' industry until we stop viewing employees like McDonald's staff.
