There is a new android app called Loch More now:

https://play.google.com/store/apps/details?id=eu.tijlb.lochmore

I don't really want to have a service just polling last known location all the time since that would be a waste of battery power.

In Loch More, you can set the polling mode to passive. Then the app will only get location updates if another app requests the location (e.g. a weather widget or navigation app), then it won't use any noticeable extra battery. If that's not enough, you can also set the polling frequency to be fairly low, then it won't use much battery either.