It may not always be the most reliable, but that iPhone in your pocket is a viable internet connection, anywhere you go. So use it! The Nexaira BC2 will turn the thing into a full wireless router, no jailbreaking required.
The $US190 BC2 is a full-fledged 802.11 B/G/N router - just stick your tethering-enabled iPhone into it via USB, and you'll have up to 60m of wireless coverage for all the rest of your devices. It won't replace your home connection - 3G data only, of course - but if the cable's ever out, or you find yourself travelling, the thing could be handy in a pinch. [3Gstore]