Google Latitude API should be updating others location on a request from the individual looking. I use it because two of my friends have Android devices (an S2 and S3). Of the 8 friends I have on there they have all been updated at or less then 4 minutes ago. I can say with great certainty they all haven't used the app less then 4 minutes ago. I rarely check it.
It works the same in iOS that's why even though I dont have it running its still using the GPS. Look in the upper right.
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I haven't found it to use more or less battery then find my friends. I think people get that idea because it shows GPS usage in the upper right near constantly. Find my friends just does not display GPS usage but it definitely uses it.
Your claim of how it works contradicts itself anyway. You say it needs to be opened for it to update then say it drains the battery. So which is it? Does the OS suspend its operation and not update and not use battery or does it constantly use the GPS updating location and drain the battery?
Maybe there is a setting in it for background updating in Android like it has in iOS?
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I can check for you on my tablet when I get home.
Like find my friends your location will be updated faster if you open the app obviously. Only time I see people not update is just like find my friends, they have it off or have turned off background updating for privacy reasons.