mobile website plugin option?

[Kolyok]

Probably the best method is to make/get a well coded responsive template.
For example lets say you would go with bootstrap (there are other frameworks but this is my favorite) then you could easily achieve the things you mentioned:

1) Only certain, select pages to be shown on the mobile device
2) Customer to only edit the one page to make changes and those changes to be seen on both the standard and mobile websites. ie not the need to make the same change twice.
3) Handle the images that are inserted by the customer for both the standard and mobile devices. ie image sizes changes depending on the device.

You would just have the usual admin panel then for the content you could do something like:

PHP Code:

<div class="hidden-xs">Your high resolution content here with a class thats hidden on phones but visible on everything above.</div> 


As for the images you could do:
1. Add "img-responsive" class to the image when you add it in the editor
2. Write some js to automatically add img-responsive class to all images that hasnt got it already:

PHP Code:

function makeResponsive() {
    if (!$('img').hasClass('img-responsive')) {
        $('img').addClass('img-responsive');
    }
} 


Then fire the function once the page is loaded/ready/whenever you want.

Note: The above example is for bootstrap. More info here.

There are a lot more possibilities (awesome stuff) with these kind of frameworks so make sure you check them out