Shame there isn't a GPS Receiver on the market which could use the US, Russian and soon to be Gallieo systems for error checking and failure warning.
There will be, just as soon as GLONASS and Galileo are reliable - or, indeed, exist. GLONASS is still recovering from being left to rot in orbit, and has very poor coverage over most of the world - less than 25 percent availability in lots of places. There are also questions over whether it'll adopt GPS compatible signalling. It's not yet stable or reliable enough to support.
Galileo is still a long way from being operational at all, but I know that GPS receiver makers are intending to include Galileo capabilities. It won't be difficult or expensive when the time comes and there's no real reason not to, but the designers aren't sure how useful it'll actually be.
R