Alright, since I bought the app I took a look and it's thankfully simple.
The app acts to emulate a bluetooth keyboard as far as the connection is concerned, this means that you need to have keyboard inputs enabled.
Here is what is mapped to what (keyboard button = app button):
b = reset
j = stop
i = pause
h = play
l = spindle on
m = spindle off
k = home
g = rapid rate increase
f = rapid rate decrease
e = feed rate increase
d = feed rate decrease
PageUp = Z+
PageDown = Z-
LeftArrow = X-
RightArrow = X+
UpArrow = Y+
DownArrow = Y-
If I have time I'll setup the keybinds in script and post it up here.
Still bloody annoying for the dev to not have any support or instructions up.
Good luck folks.