I wont take ages to explain everything there, basically the device is a 3x3 booth that you walk into, pay a diamond and select 1 of 15 options provided on how the machine will kill you, hit the button and your all set.
The deaths are only certain if your not wearing armour however. See the video for further explanation (Albeit not good explanation) on the redstone as well as the different kill methods.
Also mentioned in the video the redstone is what I like to call "spaghetti redstone" as its not the tidiest and I could have condensed it but by the end of the project I was getting lazy :).
Anyway enjoy the build!