Anyone got any advice on bike GPS units? 

I ride alone a lot and after a recent nasty fall in the middle of the Marin trail on a quiet day I realised that if I needed mountain rescue, I wouldn't have been able to give them my exact position so I could have been lying there helpless for hours.

I've looked at the Garmin Edge 205 or 305 as they seem to double as a speedo etc.  Does anyone know if they're reliable?

P.S. I managed to get back on my feet and stagger back to the carpark as it was only cracked ribs, a cracked elbow bone and some cuts and bruises, so it could have been worse!

Licko - the new Garmin 605 and 705 I think gives you the training and the gps coordinates as well, look here

http://www.bikeradar.com/mtb/news/article/get-truly-lost-with-new-garmin-bike-gps-units-12254?img=4

I use a vista c for walking. Never used one on a bike as I reckon mounting it on the bars would shake it to bits. Great for position and in the lakes/scotland gives great peace of mind as you know exactly where you are. Alsom great for planning/trackingroutes.

For emergency only, just buy the cheapest Garmin and keep a set of spare batteries. Make sure you set it to british grid.

and dont rely on it as if your in a thick tree canopy or a deep narrow vally it wont lock onto any satalites....

then again you will also need a mobile phone signal

Garmain have the etrex H which by the looks of it works better and is more upto date (its Wass enabled (see link in the link below for more info on Wass   than my basic etrex 

 https://buy.garmin.com/shop/shop.do?cID=144&pID=8705

https://buy.garmin.com/shop/shop.do?cID=144&pID=6403