Sat Nav for speedo etc.

[Black5]

I have been pondering over a Sat Nav for a while.

Not sure I can justify buying one as I tend to cycle local trails, but I could possibly use it on my MX bike (green laning).

What I do want at the moment is a speedo and a heart monitor.

Is it worth buying something like a Forerunner / other Sat Nav or am I better sticking to a standard bike speedo?

How accurate are the speedo's on a sat nav?

[Fourmotion]

I use my Forerunner on my bike, and have no problems with it at all. It has lots of different bits of data available (altimeter, gradient, calories burned, etc). I bought it for running, and it is usually bang on for distance when I run races, so I can only assume it is accurate on the bike. I've had to send one back under warranty because water got into it on a particularly rainy day, but other than that its been spot on.

[Black5]

I'm thinking along the lines of 'Fore runner' or 'Edge'.

Noticed with Edge, they don't all have heart monitor. Can I retrofit this?

Non of these seem to have maps. Can they be used as route finders etc?

[Fourmotion]

There are three editions of the Edge (possibly four). You can get it with 1.Heart Rate Monitor, 2. A Cadence sensor, 3. Both, 4. On its own maybe? I would like to upgrade to this which, as I'd like to see my rpm.

The Forerunner would be pretty useless with a map, as its not colour and has fairly simple graphics. Can't comment on the Edge. The only other facility I have used on the Forerunner is the bread crumb trail, as we got rather lost in the Lake District when fog set in and my girlfriend was in hysterics! Oh, and you can use it to Geo-Cache if you are that way inclined.