There a few other options out there. I can't speak to them since I haven't used them. I've seen some that use a laser round that is triggered by your gun's firing pin, some even offer an audible bang.
Something like iTargetPro (www.itargetpro.com) is a less expensive option, but it may be a little hokey.
LaserLyte (www.laserlyte.com) and LASR (www.lasrapp.com) both make system. I've been leaning towards the lasrapp set up because of the feedback and improvement options.
I hadn't looked at the mantis system yet however. I either think the use of a rail is a) genius or not great. I think its going to go either way. The website doesn't offer a lot of information about how it works. I'm guessing the device is triggered by sound. I could be wrong.
The upside of some of the above systems is the laser is generated within the barrel so you train to a proper sight picture at distance.