Interesting to see someone propose this with a smartphone app. There are similar products out there on the market for land lines, but they're ridiculously expensive. Here are a few thoughts from the dispatch side to both what you've present and what others have said:
-I'm assuming the idea for the app is very simple, and that's a huge plus. Most of these apps are surprisingly complex to integrate. As long as you don't push any additional responsibilities or techs like video onto a PSAP answering the 911 call, you would avoid the biggest pitfalls most NG911 techs have, which is call routing to capable centers.
-Depending on exactly how it was set up, technology would be damn near useless in an apartment complex or other multi-story, unit building. Only way I could realistically see it happening is if the app dialed a specific number assigned to the light, then 911, or vice versa. Any other systems I can immediately think of would trigger other alarms within a set range.
- A system set up in the above style would general not be advisable, while still the best option. When Joe is away from his house and uses the app, it will still at least try and dial out to his beacon, which will slow the overall call and response. That could be avoided by having it all range controlled, but that adds the above mentioned complications to the system.
-Activation by a dispatcher would be a slim to nil reality. NG911 tech is already going to be costing PSAPs more money than they have. I can see it coming through an ASAP system or similar, basically you'd realistically need some sort of separate call center to achieve that feature.
-The product will also not help with the biggest problem we have...People that have no clue where the hell they live or are. I'll still get calls where people are going to give me an incorrect address, or no address at all.
I like the idea, I apologize I haven't had a chance to read more about it on Quirky yet, but it looks promising. Realistically it's not even an NG911 tech, but something you could introduce tomorrow with the right design. That alone can put you ahead of the curve, which is moving a blistering pace right now.