Does anyone know of a boot-loader existing, or if NOOBS can interpret the position of a switch/read GPIO pins at boot then pick the partition to boot into based on what it reads? E.g. Switch in position 1 boots into Raspbian, 2 into OpenElec, etc... I know that you can change the autoboot file for noobs but that would require it to be booted already to change it before rebooting.
I know you can get SD Card Switches like this but I'm thinking 4 OS's (One for desktop, one for media, one for RetroPi and one for pen-testing) so that could get silly linking 3 of those together, and thus not portable. Along the hardware route though, has anyone had experience of making an SD switch? I'd imagine soldering your own at home could introduce a lot of latency without access to PCB Printing.
Any ideas would be cool, just need to find out before I order lots of new parts for a project :)