mforbes

Sorry, I could be completely wrong. After further research, it seems like today's audio captchas consist of distorted output from TTS engines.

I think Google's voice search already does this (feeding into audio captchas), but obviously there is a smaller crowd from which to source free audio recognition assuming that people who are both sighted and hearing typically prefer visual captchas due to environmental constraints.

Yep. They give you a little program that runs on your computer that checks your external IP address at frequent intervals and updates the DNS records when it changes. Better yet, some home routers have a configuration page where you can select among popular Dynamic DNS providers and then you don't need to run the proprietary program. My ISP-provided router (FiOS) has ZoneEdit in the list which I've used for years even before I had FiOS, so it was a nice surprise when I found it there. Just for sake of example here's a link: http://www.zoneedit.com/dynamicDNS.html

That's how mobile radios have always worked... CB, FRS, GMRS, etc. Definitely not a new problem. Repeaters can mitigate the problem somewhat.