Just as an FYI guys, it depends a lot what Android phone you have and if you 'tweak' the settings before you take off on a ride.
If you turn off WiFi, Auto-Sync and switch your data from 4G to 3G you should get plenty of time from an Android phone (presuming it hasn't got an older, worn out battery in it). I Was out for 5hrs over the weekend with my LG G4 and even with the connection left on 4G I had absolutely no issues with the battery lasting.
Then again, the fact I can keep a spare battery in a back pocket is always a comforting reassurance in case I should get close to running out.

I had pretty much decided I was going to get the Polar M450 and now I've just discovered gpx files and the concept of loading pre-saved routes to follow them. This sounds like an amazing idea to help me discover and do longer rides out and about in Melbourne.
Which devices are actually capable of excepting these pre-saved routes and giving me navigation back as part of the info on the display? (Cheapest options available please!).

Thanks