GPS tech (Garmin, Hammerhead, Wahoo, RWGPS, etc)

velocity boy
Consider the Southend ride. We didn't take the route we agreed in advance. We chose a different route and ad-lib'd it. That worked, but I would want any GPS device to allow us to be at that start line and say, "Right, let's make a new route now based on the new criteria we have.". So those units that you have to route plan in advance with, they're just not for me.

What about the Etrex (https://buy.garmin.com/shop/shop.do?pID=8703&locale=en_US)?
1,000 waypoints, 176 x 220 pixel display, 25-hour battery life, automatic routing capabilities, color screen, microSD card slot, compass, altimeter, high-sensitivity GPS receiver

It appears to let you whack in miniSD full of maps. I'm not sure how big map files are but I'm guessing you could easily cover a day's ride with a miniSD card..
Surely it would let you veer off the chosen route, so long as it was within the bounds of the installed maps?