In reply to Marek:
"...Of course, if you already have a smartphone, why not just use that? It's free."
I use Strava on my phone for all cycling, running etc. I haven't noticed the battery draining faster than usual.
If you already carry a smartphone, you're golden; if anxious about the battery, plug in an external one. I imagine you could run it for a couple of days non stop.
Wishing a good week to all, j