I would do basic obedience training.
Train him to "stay" and "sit" and "down". Practice at the door and make him stay while opening the door. Treat him like crazy with praise and treats when he does what is asked. Begin walking out the door before your dog so he learns not to walk out of the door in front of you or before you.
I really don't know much about the indoor containment systems but I'd imagine they're definitely not 100% and why shock your dog if you don't have to? I think invisible fences, etc have their place for sure. But training is essential regardless.
Any other questions- just ask.
Here's a good video: