i've seen the sam splint used as a for c spine and it works well in the absents of a actual c-collar. great for wildernes stuff as said above, i have 3 i pack in my SAR kit.
The SAM folks seem very helpful, email 'em and they may have more stuff for you.
I posted earlier that I tried the SAM C collar on myself, and it worked wonderfully, but as with any SAM application it has to be done right and in the C collar case it is a custom application. After use I use a rolling pin to get the wrinkles back out. I've actually used the splint on patients twice, once on an abducted shoulder dislocation (not common), and once as a volar splint for a Colles fracture. With enough Medirip (cheap better cousin of Coban) it works like a charm and no tape goo.
It's a cast iron b#*ch to get people to learn how to use it properly, though. I suggest letting them play with it, lots of trial and error.