MyDMX works off of key presses in user mode, so this may address many things that you may need. I haven't tested if they are case sensitive or not, but all my key-press triggers are currently lower case.
I suppose they would work just fine, provided they are programmed by the user to emulate standard keyboard input.(single key press behavior, not like a Alt-F4 for example).
Since you already have a keyboard on a laptop, there's no reason to NOT use that interface already there and it would save you money as well. I know for a fact MyDMX works with my wireless numeric keypad, provided the keypad isn't giving me grief! If lighting on the keyboard is an issue(it's not for me, the MacBook Pro lights the keyboard in low light), a USB LED light could address that issue.
I think it ideally comes down to how the XKeys devices are programmed by the user would most likely ultimately determine how the hardware would work with MyDMX.
My thoughts: You already have a keyboard on the laptop. Use it. Have MyDMX learn the triggers in edit mode, and it will TELL you in Edit and USER mode which keys are programmed for which scene.