hello all,

i'm planing to buy 4 gsm phones for me and my friends to use voip. most of the time we are capable to have a wifi zone. i couldn't reached to satisfactory information about seamless convergence from wifi to gsm (i hope via gprs) switching. also, i'm planing to get sip ata devices for home and office.
if i write a list of my needs:

1) gsm phone which can support voip-out, voip-in from gprs.
2) same as #1 but with wifi. seamless convergence from/to wifi and gprs during voip call.
3) acceptible roaming for wifi zones.
4) sip to sip calls.
5) sip ata devices (without pc) (grandstream handy tone 386 seems satisfactory)
6) bluetooth (if possible)

7) built-in gps (if possible): (sorry this is off-topic.)
if possible run skype additionally.

nokia e or n series mobiles seems to support these but not sure how good they are.

any advice, comment, experiments welcome.