Hi,
This was probably a "Power Tap" power measuring device. They are a part of
the hub and are yellow in colour.
I hope this helps.
See he
http://www.cycleops.com/products/powertap.htm


"Eric Hill" wrote in message
...
The other day I saw a guy riding a rear wheel that had some kind of
design object or technical doodad that looked like a squashed tennis
ball, in color, on the non-drive side of the hub, outside of the spokes.
In your best mental mallrat voice, "I was like all, 'huh?!'"

-eric