I see the biggest challenge to using PerlMonks on a small device (aside from the difficulty of typing markup and code on an alpha-centric keyboard) is the fact that the nodelets at the side take too much width away from the main section.
Rather than a dedicated app for each platform I see more value in (and have thought about this before too) allowing a URL to have a rendertype=tiny, or something along those lines.
As for what that would do: All active nodelets would render at the bottom (below the main section). That way I get more width for what counts. Hand in hand with that, the Nodelet Settings page could have a column dedicated to minimal displays to allow me to pick and choose which nodelets I want to see on my screen-size-challenged device, independently of the standard settings used everywhere else.
Of course what this requires is a lot of work, and it's hard to find a volunteer who knows the site's internals well enough, and is motivated enough to see a project like that through to the end, and has the time.