A colleague at work has parents who keep bees, and has instrumented their hives. See here for the top level, and the webcam. As well as being jolly fun, its also quite useful. Looking at the weights of the hives, especially through the year (bottom pic) you can see how they are doing over winter, when the flow has peaked, and so on. There is also a bee counter (in units of bees per 5 mins, averaged over the day, I think; its done by only allowing the bees in/out via a set of holes, each of which has a photo-detector above them). The activity is very different to what I would expect, in that there is no rape-seed peak in the summer.
I’m sure Olivier can be persuaded to describe his set-up in more detail if any bee-keepers are interested :-)