How about a gps based one?
http://www.holux-uk....-245.php?it=173
I've got the 260 which has been very good (it was a fair bit cheaper than it is now though)
Do you have any of the add-ons? I had never heard of them until I saw your post, but have had a look at the Pro, with the cadence/speed sensor. It looks very good value compared with other gps ones.