There are a few of us using a Terratrip T006 on this page http://www.donbarrow.co.uk/terratrip_te ... eters.html we bought them from another company the name of which escapes me. Then a few are still using the magnet on the hub or wheel, but I prefer the sender as it's far more reliable & robust.
Think the other company was gprdirect but if Simon reads this he will confirm.