Like an X-ray of London's underground system, the Live Tube Map from Matthew Somerville, uses a Google Map with a marker above every train on the system.

Watch for a while and feel the sympathy build (only a little given there's potentially a strike tomorrow) for the people who have to manage the traffic on the tube system.

It's also a brilliant and hopefully well-learned lesson in the benefits of opening up data so developers can get their mitts and imaginations to work on how it could be used. And if this is your bag, check out the events for the £5m Collaborative Metadata R&D Competition that I've been working on with the Creative Industries KTN.