Most WiFi routers have a browser-accessible admin interface (usually supplied with default passwords, that need changing...) showing connected clients. There is not, usually, a way to "kick them out", but there is a "MAC security" option. Not really so effective, since tools exist that allow modifying MACs of WiFis, but you can tell your router to only accept connections from your laptop's MAC address.
Since the interface is HTML/JS, it is naturally multiplatform. To "kick someone out", though, you need to reset the device (this also can be done remotely), thus kicking everyone out, and being then the only one to be able to get back in again (in such a scenario, also change the WiFi password!).
By default, most routers expose the interface on their own LAN IP, so you need only point the browser to, say,
http://192.168.0.1/ , or whatever your gateway address is.