We provide a multi-building wireless network to the department (in addition to the university wide wireless network provided by the central IT people). For reasons beyond the scope of this entry, we don't have much innate visibility into how this network is doing in the various places it exists. This means that our only current ways of finding out whether or not it's currently working right somewhere are to wait for people to notice and then report problems (which doesn't always happen) or going there ourselves. We've recently decided that we'd like to do better than this.

The obvious thing to do is to put some boxes on the wireless network at various (physical) locations, and then have our monitoring system check to see that they're still visible (for example, through pinging them). This is fairly brute force but it's also a good end to end test; if we can reach these boxes over the wireless network, they can see the network, associate with it, and contact our DHCP server to lease addresses.

We need these boxes to be inexpensive, because to be useful they'll have to be in relatively exposed locations where they might walk off. We have strong opinions that they need to be wall powered, not battery powered, because we don't want to be going around every year or so to re-find them all and replace their batteries with a new set. Ideally they'd do something useful, like report the ambient temperature around them. Unfortunately we haven't found anything that combines these three attributes together; inexpensive wifi temperature sensors seem to all be battery powered, for example.

What we're currently experimenting with is wifi controlled smart power plugs. These tick two out of the three ideal features; they're generally inexpensive, and they're powered by the wall instead of batteries. They're also available from reasonably reputable brands, which helps give us more assurance that a unit isn't going to burst into flames some day, although in actual deployment I suspect that we'll tape over their power outlet with a 'do not use' label.

(If you get the right model, you can even get Unix tools to talk to it.)

We've only just put a couple of these wifi smart power plugs on our network, but so far they do seem to ping consistently. We'll have to see if that keeps up, but I'm cautiously optimistic. Of course I'd love to discover a better option, but I honestly suspect that there isn't any (for example, I can see why hardware designers would want to avoid wall power if they can).