VOIP is teh best solution across the board, but the only thing lacking is the capability to be "always on" in order to receive calls, which is where the wimax/3g concept comes into play... these are functional with dongles (but make life difficult when wanting to keep the pandora in a pocket because NO mfg thought it would be smart to make a wimax/3g dongle that would be small enough to plug in and be unobtrusive to the chassis of the device in question... wifi and bluetooth dongle mfgs have figured this out, stronger technologies, not so much. Nor has it become anywhere near commonplace for wimax/3g-enabled sdio cards to be on the market (which is also a shame... I'm sure cellular mfgs are either stonewalling or paying off sdio mfgs to keep things moving as slowly as possible).
Summary: most viable solution is voip+wimax/3G/4G (once technology is nicer to handheld devices) via mini dongles or sdio cards...