Back in my day we didn't try to watch a game on a 2" screen. We went into the nearest bar and bent the bartender's ear until he put the game on. Not only that, they sell beer there too! Though, sometimes you actually have to talk to other people!
I guess you didn't take two seconds to read what the Slingbox does on Wikipedia
I'd mostly be using it to watch games on my PC when I'm not home. Very seriously doubt I would bother paying the additional $30 for the mobile app.
So for my purposes, it's either
(A) $125 for MLB.tv every year, and then have to proxy to even use it, or
(B) Slingbox for $179 once, use anywhere any time.