If you find yourself in an expensive hotel without the funds to cover that three-course seafood buffet you've just demolished, you may not be led to the back of the kitchen to scrub pots and pans after all... you could be off to the gym instead. Crowne Plaza Copenhagen Towers has installed two electricity-producing bicycles which are connected to the hotel's main electricity supply. Guests who pedal hard enough not only get a dose of environmental feel-goodness, but can also score a complimentary meal.

The energy produced is stored in a battery on the bikes and then fed into the hotel's mains supply and you can monitor your progress on an iPhone attached to the handlebars.

It's estimated that pedaling at 30 kilometers per hour for 60 minutes will produce about 100 watt hours of electricity (which would run one 100W bulb for one hour), so reaching the goal of 10 watt hours to earn your free meal should be comfortably doable in under 10 minutes.

If the pilot scheme is successful, the power-bikes will be rolled-out in the 21 Crowne Plaza hotels in Britain.

OK, so it's easy to be cynical about this "world first" as a bit of a gimmick, and your pedaling efforts are hardly going to offset all the electricity you use during your stay. But it does raise awareness about energy use and promote alternative sources of energy production that harness kinetic energy, and it's hard to argue with that.

The 366-room hotel's green initiatives also go way beyond exercise bikes. There are 2,400 solar panels installed on the Crowne Plaza's facade and it uses low-energy lighting and a groundwater-based cooling and heating system.