Google Use to have an app that worked in conjunction with Maps called LATITUDE, where you could add friends and it would track them in google maps. If someone didn't allow real time tracking you could "ping" them and they could respond to the request. I miss that app since all of us use our phones for music and you'd hear an audible ping come in and know someone was looking for you, great option when you're meeting a group and someone was running late.
I'll have to look into this Glympse app.