Fing is a great (and free) app for monitoring traffic on a wifi network.

I highly suggest grabbing it from the app store and just playing around to see the cool features.

Try starting a http server on your local computer. This one liner will do the trick:

ruby -run -e httpd . -p 8000

Then in the Fing app, find your computer and click Scan Services. You should see it list port 8000 as being open.

You can also check out all the devices on your home network and see if any have a high % of packet loss. Devices dropping a lot of packets are possible security vulnerabilities in a network.