O2 (UK) Telefónica O2 had a long-standing relationship with Arsenal F.C., being their shirt sponsor until the end of the 2005/2006 season. In 2005, a three-year deal was signed that saw Telefónica O2 become the team's exclusive mobile communications partner. O2 were the main sponsor of the Channel 4 reality TV show "Big Brother" from its second series (as BT Cellnet) in 2001 until its fourth series in 2003. They also sponsored the spin-off shows "Celebrity Big Brother 2" in 2002 and "" in 2003. In total O2 sponsored five series of the show. O2 sponsored music festivals, the Wireless Festivals, from
O2 Money application for Android and iOS devices. The application will use NFC technology embedded in a phone to access money banked with Barclays via O2. O2 began trials of NFC technology in , with 500 individuals participating in the trial. The individuals used a specific Nokia handset to make payments at selected retailers, and travel the London Underground with transactions made via Barclays. O2 has since been in discussions with large retailers, such as Tesco and W. H. Smith, for the deployment of the necessary electronic point of sale units, and with handset manufacturers, such as Apple and Samsung, to enable