Since you made this Android vs. iPhone
I had a Samsung SIII and Samsung Galaxy Tab 3 7" (x2). I was going to mount one of those in my TB, but I got fed up with Android. I ended up trading my SIII and both tablets for an iPhone 5s and a iPad Mini w/Retina display. iPhone is more user friendly and (jail broken) just as customize-able as Android. What Apple does, that takes it leaps and bounds above Android, is the OS. iOS is fantastic in that everyone gets the new software at the same time. My Andoid was running 4.2.2, while 4.4 was already out. Android has to go through the creator, the phone manufacturer, then the carrier (all of who add crap I don't want or need) and then, MAYBE then, can I get it to my phone. I hear they are starting to come out with clean Android OS versions, but I have yet to see it in fruition. The one thing I wish Apple would do is install a dedicated GPS module that would work without a data connection. Then I could mount my iPad Mini in the TB and have everything I ever wanted or needed. I shall step down from my soapbox now...
As for the app, I don't have any experience with them, but
Engine Link - OBD II vehicle monitoring and diagnosis looks like it could be good. It's got 4.5 stars, but only 11 reviews. That's the one I would check out, if I was going to buy the ELM adapter.