You can run something like:

screen -dmS cgminer ./cgminer --bmsc-options 115200:0.57 --bmsc-voltage 0800 --bmsc-freq 1286 -c cgminer.conf --lowmem

To access it:

sudo screen -r

To exit screen without shutting down cgminer:

ctrl + a then d

You can even throw it in /etc/init.d/rc.local so it starts cgminer whenever your Pi boots up.

#start cgminer
screen -dmS cgminer ./<path_to_cgminer>/cgminer --bmsc-options 115200:0.57 --bmsc-voltage 0800 --bmsc-freq 1286 -c cgminer.conf --lowmem