Cellnet/British Telecom (BT) has been active in the area of GPS/GSM location and application research for over five years. Cellnet/BT have undertaken considerable development and field trials of various GSM methods for location positioning, which have resulted in several patent registrations. Recent R&D projects undertaken by the Mobility engineering team at BT Labs. include MOSA (Mobile Social Alarm) and City Guide using GPS positioning data to deliver value-added applications and services for both the general public and business users. A critical factor to the successful development of innovative value-added services is co-operation with partners, to promote and evolve open standards for GSM location.