can this be used to debug non-arm based ucs? routers and modems? im 
wondering because i am trying to find a cheap solution to modify some 
firmware.

You can use the STLink together with a OpenOCD. Many chips are 
supported. If you use a packaged version of openocd and your chip is not 
yet supported, look at  git://git.code.sf.net/p/openocd/code an the 
pending patches at http://openocd.zylin.com/#/q/status:open