It can be done, but how much technical expertise you need to have depends very much on the brand and model number of the router that you are using. For example, there are a couple of routers which have their own IFTTT channel and make this very easy. But with most routers it’s pretty tricky.
Take a look at the community FAQ on different methods for presence and there are several threads linked to from there that discuss various Wi-Fi-based methods.