I quite like the idea of LED indicators and am tempted to try a set of these:
http://motrax.co.uk/index.php?mod=product&id_prd=114 
They have a tip at the end to try and aid side and opposite visability.....
I'm just too tight to pay the £30 rrp
Cheers - Frank
PS - I think I'm right in saying that one side of a bikes system can be changed to LED without having to fit a resistor (or whatever it is !!!)