A couple of thoughts here:
1. Keep your firearms in a @$(@$ safe unless you can put your hand on them within a second or two at any given time. If you can't physically control it at all times, it needs to be locked away.
2. Don't give the safe combo to your children or anyone else. Don't let them watch while you open it.
3. Don't buy a crappy safe. Hotel-style 4-digit lock codes won't cut it.
4. Once a weapon is out of the safe and you're not there to witness it, it might as well be stolen. In other words, what you want to watch is the status of the safe's door and not the location of the individual guns. See #1 and #2.
5. There are already many wireless solutions to track door status. That NinjaBlocks appliance on HN the other day comes to mind. I don't want to invest in an entirely separate system. I want something that integrates w/ my existing home security.
6. You're not going to get much milage with the firearms community by calling them "assault weapons". That's a loaded term and I don't like it. Your potential customers are guys like me: considerate, caring people who happen to enjoy shooting guns and who own a few, but want to keep their collections safe. I'm not assaulting anyone and your use of that term is enough to keep me from buying your product.
7. You're wrong about mass shootings. Most, including the most deadly (VA Tech), were committed with handguns, not long rifles.