score:1
There is an app called gpslogger that will provide some the functionality; it covers the part that "could easily be written" to push the location.
This Android app has the ability to periodically post your phone's GPS position in many formats. The frequency of posting may be customized. If one had access to a web site that would accept HTTP requests, this app could feed your location to that web site, and that web site could display a map. This is not the desired solution since the question is about finding:
..a service to plot (the locations).
As a substitute to getting your positions onto a tracking map on the web somewhere, gpslogger has been extended to send email, but this version is not on the play store, so getting working requires being an Android developer. This version may some day be extended to work with Spotwalla, but doesn't currently do that.
There is an app called Bubbler GPS Pro ($9.99), that will upload to Spotwalla. The lite version only allows 5 stored positions, so isn't useful, except to see if it's worth buying the Property version. I'm not sure how Spotwalla makes money, but they say they don't charge for their services, so this appears to be a $10 one time cost. Or possibly free if the points persist on Spotwalla and you don't care to save them locally in your phone. The pro version allows pictures too, so might be worth buying for that feature.
Upvote:0
Since your own answer allows the possibility of having access to a webserver, you might consider ΞΌlogger. This free (as in freedom, it's GPLv3) Android app comes in two halves, an on-phone client, and an on-server viewer, apparently written in PHP, for the uploaded tracks.
Disclaimer: I have no connection with the project, I just fired up my fdroid client and did a bit of searching.