So I've just been watching on of those endless re-runs of 'Top Gear' on Dave (a UK TV channel). In it, they had a feature where Jeremy Clarkson operated a car's central locking from a massive range by placing it against his head. It didn't work when just held in his hand. There are various theories as to why this works which all seemingly make an appearance on this site. I've attempted to summarise:
1) When the remote is held against the head, it is higher. This gives a better line of sight and allows more RF waves to get to the car as they've got a better 'angle of bounce' on the Earth's surface.
2) The head amplifies the signal. This would be due to 'constructive interference' in the skull. I'm dubious.
3) Holding the remote against the head boosts the electrical currents flowing through the chest and hand, which then radiate a signal "roughly four times as powerful".
4) The signal emanates at right angles to the 'head' of the key. By holding it against the head, the key is reorientated so RF waves go more in the direction of the receiver.
5) The head 'retunes' the signal slightly. According to this idea, as the remotes are mass produced, they often send a signal at a frequency just off the desired range. When held, the hand will alter the signal towards this range. The car manufacturers take this into account when tuning the receiver. When the remote is placed against the head, the signal is retuned even more than when it is placed against the hand, so the receiver is much more sensitive to the RF waves.
I'm not sure which one I believe. They all seem so ridiculous! I think I'll go with Occam's Razor- the simplest explanation is usually the right one. So that'd be the height thing. Jeremy Clarkson is quite tall after all.