To me the thing that makes the most sense is a single good wireless microphone with sufficient decent range.
This one for example claims 20 meters. That may be enough for some people. Obviously not, if you live in a mansion
http://www.revolabs.com/pdf/product_manuals/xtag_datasheet.pdfFor me, the amulet range is sufficient for all the areas where I would actually use it, it would be nice though if it were something I could wear, like on a lapel.
A "wireless microphone system used for live music" would probably work, but you still need to figure out how to deal with multiple inputs and if you need a gate etc...
I think you can actually use a 5.8Ghz (or even lower Ghz) phone system, or a wired phone system. You need to handy to do this though, to get the wiring right, and to fool the phone into thinking it is connected to a live phone system, and it needs to be a phone system that you are not already trying to use as your phone (I think).