Hey @janek, I'm currently developing something that should allow you to show a heatmap in the Node-RED dashboard. Had an issue with that last night, but @dceejay already proposad a solution. If that works, I hope to be able to offer you something next week ...
About the frame buffer... It would be interesting if you could post here a diagram of your setup: how the sensors are hardwired to your Raspberry (or perhaps other hardware in between), which programs/scripts you call with the exec node, ... And an export of your flow of course. Then it is easier for us to know what you are doing, without having to read all the information on the Github page.
