Mobile payment systems may be gaining only gradual steam in the US, but over on the other side of the pond, Vodafone UK has launched a broad new campaign to integrate smartphone technology where Londoners may need it most -- in the back of taxis. As of today, many cab passengers will be able to charge their smartphones in transit, thanks to a wide range of chargers that the mobile carrier has installed in more than 500 of London's iconic black vehicles. Vodafone is also rolling out a new payment scheme today, whereby cash-strapped travelers can text their cab's license number to a specific code, allowing any owed fares to be charged directly to their phone bills. The system certainly doesn't sound as elegant as some of the NFC-based operations we've heard about, but it still beats having to navigate your cab driver to the nearest ATM, with the meter tick-tocking away.