I have been asked about finding a system that basically allows a small company to take bookings, as simple as possible.
They print a magazine and want to record the location of adverts and currently they use printed sheets, where they have an outline of a page and then draw a box (a few standard sizes) in the right location and name it.

They want a system that can be used on desktop and mobile (probably iPad).

My thought was to have a website and the standard sizes displayed as divs and have them be dragable on the page. They would then need to be able to label the boxes. Probably saving all the details to a database due to the amount of data that will be needed each week.

I assumed this would be a fair common thing, but I cant seem to find anything. Possible i'm searching the wrong terms.
Am I way over thinking it?

I have found a few jquery examples that do bits and pieces of what I was thinking, but nothing near complete.

http://www.elated.com/res/File/articles/development/javascript/jquery/drag-and-drop-with-jquery-your-essential-guide/card-game.html
http://papermashup.com/demos/jquery-drag-drop/