Looks like you have to pay for a subscription, but MLB does have an Android app that would do what you're looking for
MLB.com At Bat 11 | MLB.com: Mobile
At Bat 11 features include: - Access your
MLB.TV subscription to watch live
out-of-market games or watch the At Bat.tv Free Game of the Day
I saw this app, but I wasn't sure what out-of-market games meant. So, does that mean if you are capable of watching the game on your tv, you cannot watch it on your phone/computer?
Plus, MLB.TV is $20-25/month ($80-100/year), plus $15 for the app... I guess I haven't priced out the other solutions, but that seems like quite a bit just to have the ability to watch tv on your phone, unless the team you want to watch isn't the home team (or games are regularly broadcasted by your Television provider).
The other options would have access to anything you can watch on your TV and DVR (slingbox, hava).
EDIT: I just noticed MLB.TV has a mobile only version for
only $40 a year...maybe not such a bad option...