In the case of mobile phone and Vita/PSP, you could always make use of TV-out functionality. My vision isn't great, but I'm thankful that it's (still) good enough to cope with text and UI elements on a tiny screen.
Speaking of — Lemmings was indeed awkward on the small screen. There's a zoomed-in view, but it's still fairly small and it results in you not being able to see much of the level. Playable, sure, but not especially comfortable — I'm far more inclined to boot up the original on my computer.