i have been looking for the pricetag to drop on either the zumo or the tomtom rider (which comes with bluetooth headset ((only discernable difference?)) i have seen a couple zumos go for $550 on ebay, but the low price for either one is still around $700. these units are both waterproof and full of the same features, incuding mp3 and cellphone (dont even want that death sentence) but i would settle for a simple yet durable stripped down version that just let me know when i could be on a twistier road just off the one on im on or get me unlost without all the cellphonery and even the tunes which i would use and get used to having but dont feel the need for now.
but my recommendation would be whichever one you can find cheaper- the zumo or the tomtom rider, but remember that you will need to buy the headset separately with the zumo.
good luck
-KK