You would need to have one Pi responsible for the Blinkt! and the other Pi’s communicating via it. There are myriad ways to do this but a simple Python Flask app might be the easiest.
Yes, that was my first idea: 1 RPi connected to the Blinkt! and the others sending simple UDP packets to it with state codes.
In that way, however, we have to make some awful assumptions:
the RPi connected to the Blinkt! is immune from failures (in fact, if we assume it can fail, we cannot tell if the state shown by the Blinkt! led is correct or not, a priori)
the network connecting the RPi in the cluster to the Blinkt!'s RPi is always up (in fact, if we assume it can be down, we cannot tell, for example, if a led is off because of a RPi failing or because of the lack of UDP packets due to network problems).
For those reasons, and for others, I’m not so happy with that solution.
I’d like to have independet led connected to each RPi.
Do you have such a product, beside Blinkt!?
It’s possible you could use a micro-controller to act as the arbiter, and demultiplexer in this sort of setup. If you assigned each Pi it’s own IO pin and the state of that pin- High/Low- determined what displayed on the LEDs then the micro could read those pins and update accordingly.