BattClock shows Time and Battery percentage above the top bar.
Very small in memory: 1 Kb in memory (check it with a task manager)
No CPU usage: 0.00 % CPU usage, check it with a task manager)
Very small on disk: BattClock.exe 17 Kb on disk, BattClock
TouchLockPro is designed not to interfere with running applications and is a multipurpose locking application. Other locking solutions are often specific for locking only incoming calls/SMS. A lot of locking solutions also place a (transparent looking) Window on top of the running application (e.g