Anyone know where to get an internet connection tester?

I work as a cable installer, and occasionaly I run into a situation where I'm installing internet service, but the customer has no computer. Often times they just need the connection for their X-box 360 or ps3, but sometimes the connection fails and I have no way to find out where the problem lies without something to test for a proper internet connection. I'm looking for something cheap that works. Doesn't need all the bells and whistles, just let me know if the connection is good. Thanks in advance.