How to tell the type of device by MAC address?

I have a friend who uses our Wi-Fi and one of his apple devices showed up on our list of people connected. It shows the MAC address and I found a site that told me it is in fact an apple device, but doesn't say anything else.

Is there a way to find out what exactly it is such as an iPhone, iPod, or an iPad? I want to figure out because he didn't even come over today and it showed up.

The IEEE maintains a list of the manufacturer codes - the first half of the MAC address.

The last half is unique to the device. If you can tie the device to a MAC, or assign a specific IP address on your router for it. There's no list. You will have to do some detective work.
If you assign a "dead" address like 127.0.0.1 - then your 'friend' won't be able to use your network to access the internet.
He might say " I'm having trouble using my iPhone to connect to the net". Or you may need to be a little more subtle.