Emu Messenger could be the best complete solution so far
From veterans of Apple, Google, Yahoo! Messenger, TechCrunch and Siri the Emu Messenger was born. But what makes it special?
Unlike other offerings out there this completely and seamlessly makes communicating and planning one simple process. A message about meeting can have a link to the restaurant which you can book at a touch. Then see how near the other person is on a live tracked map so you meet on time. And if you're asked to do something else when you have plans, just defer to when you're at work and it will be smart enough to know when that is. Check out the video here to see it in action.
So to summarise Emu can track friends live using its Marco Polo feature, book tickets using its Movies and Restaurants features, update your calendar using Scheduling and alert you with Snooze, and it'll work with Push To Talk for voice dictated messages.
Emu is out now for Android and can be downloaded here.