Whatever it's going to be implemented as (if it's even MEANT to be implemented) I'm pretty sure Apple will not apply the screen into anything that is bigger than the screen itself. Going by Apple's past and present use of "non-tacky" design, they are not going to produce a screen with rounded edges if they were not going to take artful advantage of them.
If you notice, all screens that share this design have covered the entire surface plane where they were used. They are not going to tack this onto the back of an iPhone or MBP because it would look... TACKED on.
Therefore, the remote, the watch and the shuffle seem to be the most viable products that have been hypothesized here. But even then, you have battery power to worry about. It'd be a pain in the ass to have to remember to plug in my watch every night (as well as everything else!) The remote however may go under the knife and get rechargeable batteries instead and possibly even use the iPods connector to recharge, and update the TVguide within the remote.