The Nokia N95 is on KPN's network and the TyTnII (MDA Vario III) on T-Mobile's.
Apparently it only works well when the phones are set to use the GSM instead of the UMTS network.
What surprises me is how well it works.
Most mobile operators considering location based services are thinking in terms of checking every several minutes.
Whereas this product seems to check every one or two seconds. And in effect notice every hop from cell-tower to cell-tower.