Well not really a peculiar one as MJ replaces some plugins like metatemplate.
If you use it to control the output of your website depending on the client visiting it, you should be able to control all outputs.
If not, we will need to have mixed solutions, one for mobile, one for facebook for instance and maybe another template for something else.
You should go all the way and propose a solution to tailor MJ according to specific template needs when displaying a website, the most general one being a display in facebook apps.
I use metatemplate for now which is very good at displaying specific templates according to the browser, the referrer or the device visiting the website. But your solution is more specific to the required task and seems promising with extensions, this is why I suggest this move