The cost of the yellow tube will be the limiting thing, that an you don't actually see a direct result from carrying one.
With a radio, you have a handset and can feel like you are doing something and getting a result, as well as having personal input.
The yellow tube just sits there sucking up your and everyone elses wifi messages and forwarding them when it can. Most won't see a direct result and a lot of the time you will just be a conduit for other peoples messages, having no actual input yourself you get no reward. Not much different to re-transmitting a message on a UHF, but without that personal input people won't feel a personal connection and will value it less.
For a emergency service, then I can see funding, the need and a maintenance schedule being adhered to. But for personal use...Maybe it needs some sort of feedback via an app loaded into your mobile device, 'Congratulations, you have forwarded xxx messages' or something when you are part of the chain that led to a rescue, otherwise it will just sit there and be neglected, not maintained or just left in the shed at home.
Many wouldn't be keen on the idea of a swarm based tracking system being fitted to their vehicle from the factory either. I did have a rental in the US that had a system that tracked you and notified 911 of your location if the air bags deployed. Not too many tin foil hat wearers were lining up to hire that one I'd imagine
Don't get me wrong, I think it is a great idea and could be fitted into something the size of a Spot tracker. I'd even be interested in getting one, hooking up external power and an external aerial to extend it's range. It all comes down to the $$
