I have uploaded a new node to npm, node-red-contrib-random-event-generator.

From the README:

This node generates events (messages) at intervals drawn from a random distribution. By default, an exponential distribution is used, where the probability of a given interval between events is an exponentially decreasing function of the length of the interval. This is the behaviour displayed by radioactive decays, noise in electronic devices, and other physical phenomena. Alternatively, the probability distribution can be chosen to be uniform in a selected range.

The node has been useful in testing the operation of message queues and in Monte-Carlo simulation of physical systems. It can be downloaded from npm, GitHub, or the palette manager.

I am grateful to @Colin for advice on an early version of this project.