I think it be cool to have a small routerboard with 2x ethernet and a wireless radio. Kind of like what aruba has.
http://www.arubanetworks.com/products/rap-2wg/
It doesn’t have to have a big cpu or anything crazy but something small where you could deploy them cheaply in the field as a portable router or vpn device for end users.
Is routerboard 951-2n too big for you?
I didn’t even notice the 951 was as small as the 750 but with wireless in it. Thanks for pointing that out. 
I was thinking the exact same thing, something to allow hackers to drop in between network interfaces.
Say you wanted to add a mikrotik router to something… say a cisco HWIC-1FE… you could unsolder the pads from the magjack connect to microboard resolder other end. this would bring life to all the 1841’s or other wics that have adsl and isdn cards to make an intergated soltuion.
Or another would be to integrate directly into a adsl modem.
Or inline cable firewall? with SPAN??
Or a network card.
It would be like a integrators board pad access to the mii interfaces.