How about some smart ass developers out there create the device instead? i personally feel that if the game providers develop the device required for checking RTP, what is the guarantee that they wont be accused of developing the device in a way it will favor them and their business?
They can't
Why? it's a business scheme and most of provider will always closed their source code. If anyone, know their source-code there could be have some leaked hacked to their game. That's why, I the suggested only can be made by the provider.
Imposible for individual person, because they will never share the source-code.