I have had the PetSafe wireless unit for about 5 years.
It works very well. My dog is a German Shorthair and she is prone to wander.
I put the base unit inside the house at one corner. That gives her the most radial range but keeps her off the driveway.
I am on wireless receiver #2. They eventually croak. Batteries last about a month. You can get them at Lowes for about 10 bucks for two if you need them badly.
I created my own collar by using a hole punch and razor blade to mount the wireless receiver. The stock collar is pretty flimsy.
The unit will beep a warning at the dog when she gets to the edge of the range. The shock is pretty stout but they get the point quickly.
Being able to let the dog outside with WAY less worry is great. Unfortunately you still have to be aware of your surroundings and what can wander into range. Like skunks, woodchucks, and porcupines.