Internet testing device?

We're seeking a small inexpensive device, like a cable tester, that will simply check for internet connectivity.  Obviously, we could use a laptop, but that can be cumbersome... We'd like a simple device that we could plug into any port on a switch, for example, and know if we're getting an internet connection... (Shall I define "internet connection" ?  Maybe if it was able to obtain an IP address... or was able to ping the source...  

Thanks...