Hi John -
Yep. Tried PocketShield (good little program) but I had issues with the light sensor not being sensitive enough to unlock my device a lot of the time (a common issue for TP users apparently). Tried tweaking the program as well to no avail.
If you live/work in a bright enough place, PocketShield is a good solution in my opinion. Just no luck with it over here.
TouchLockPro seems to be a very lightweight program as well (I recall it being more memory efficient than PocketShield, so that's a plus too).