Another bright idea..

[yenrod]

http://www.gadgetsandgiftsuk.com/show.asp?id=1235&cat_id=111

Though, for presta valve users you'd have to get one of those small adaptors but I reckon they'd be worth it - anyone with any experience of these

 

[twentysix by twentyfive]

Yep - could be very useful . But they do say for use on private land only. So I guess they aren't legal on the road. Nevertheless for us vulnerable road users I'd say ignore that technicality - just as we all used flashing bike lights before they became legal.

 

[mickle]

They do look great but are incredibly unreliable in my experience.