Alex,
It is a gonodactylid, but for a positive ID I need some more information. First, do you have any idea where it came from. Hawaii, Indo-Pacific, Caribbean?
Second, what color are the meral spots? Don't worry about the white rim and dark spots - just the center - white, yellow, red, blue, purple, etc.
Third, can you get a shot of the telson and uropods (tail) The dentition of the telson is one of the best traits to use to identify stomatopods.
I won't venture a guess as to identity until we get some more information. There are half a dozen species that fit this general color pattern.
Roy