Cellphones that Work Everywhere?

spoonist asks: "The vast array of available wireless protocols in the US is quite bewildering: CDMA, TDMA, GSM, AMPS. I spend most of my time in urban areas. Major providers appear to be rolling out GSM, so that seems like the way to go. I also spend a lot of time hiking and climbing in rural areas and like having my mobile phone in case of an emergency. My ancient analog phone gets a signal in all but the most remote of areas LONG after friends' digital phones loose their signals. Are there any dual mode mobile phones that can talk both GSM and AMPS? Also, I occassionally travel to Europe. From what I understand, GSM in the US uses a different frequency from the rest of the world (WHY!?!). Are there any phones that talk European GSM, US GSM, and AMPS?"