Depending on how the client is configured, it may or may not send the hostname when it makes a DHCP request. But, as the example shows, you can access it via the MAC address. On my own home set up, I use the hostname field in the dhcpd.conf so I know which machine it is (livingroom-tv, my-desktop, wifes-iphone, etc) and depend on the MAC address hardware ethernet
option to determine which machine is actually getting that particular IP. DNS is handled separately with a fake domain (my.house) because only a few machines actually need DNS entries (for me/my convenience) and is not integrated in any way with DHCP. Almost all of my static-dynamic MAC address based IPs are given out to control access - I have a VERY short lease time, and when the kids need to be blocked from access, I simply change their default gateway or point them at a second DNS server that restricts where they can go/what they can do (ie, on their phone facebook.com may say "you should be doing homework!" :) )