I think this is an extremely important feature that should be added in as soon as possible. The ability to know whether a member is online, (in my alliance), would be used solely for the purpose of benefiting the alliance not causing problems for others. I prefer to have active members in the alliance and this would help out a lot. It doesn't necessarily have to say last logged in... it could just be a few days or so and it could just highlight the name or something to show ok this person is still playing and didn't just get his phone stolen so he can no longer play lol God forbid,
Just my 2 cents