Today Volker (aka vosi) pointed me to some intresting links regarding gsm network security. I guess this brings a new scenario into my mobile modding and hacking hobbies…
thanks vosi !
I’ll write back again after i have digested this new info and made something out of it… cheers

(Mobile) GSM Interception
GSM Interception System
by Scandeas
http://scandecas.com/GSM/PrintScreen1.jpg
(Stationary, passive)
GSM Sniffer
PGIS 900/1800 Passive GSM Intercept
by PGIS
Off the Air GSM
Interception
By: Shogi Communications Ltd.
(Passive) GSM Interception
GSM Monitoring System STL-5020
Secur Telecommunication Ltd.
(Active and passive) GSM Interception
(Restriced Access) GSM Monitoring systems
GCOM Technologies
Interception of cellular networks
GSM Workshop
GCOM / SypZone
GSM Interception
GSM interception System
Accelerated Promotions
Interception of cellular networks
GSM Monitoring Seminars
GCOM/Spyzone
GSM
Comstrac
GSM
DPL-2060
DPL Surveillance Equipment
COMP128
SIM Clone KIT
Access Technologie

[...] This can EASILY be implemented with a GSM sniffer on a stumbling scale (move while you scan) or there a full edge commercial applications to hook up the a carrier and profile the entire network. [...]