I know, it's New York, but hey, they seem to have similar problems over there
With the party season starting, finding a cab is getting more and more difficult. So I was very happy to stumble upon a new App - Hailo - that seems to work (according to comments) like a dream. Download from I tunes and it calculates your position when you hale a cab, cabbies nearby are alerted and someone will accept and get in touch to let you know when he will arrive. Sounds brilliant!
Payment is equally simple, either by card or cash, and they will email you a receipt. Whether they will make it south of the river is another question, though. I will give it a go.
(For more London Apps see here)