The question doesn't specify a specific DHCP server to use, so I'm going to be a little cheeky, and offer up an alternative to Microsoft DHCP, which, judging from the comments and from looking around a little myself doesn't seem to be able to do what you want.
From a cursory reading of the manual page for ISC dhcpd (the Internet Systems Consortium DHCP Server), it would appear that this server has the configurability you're after to do this - specifically see the example under the "Subclasses" section. The example won't work as-is, but it demonstrates that the server has the configurability neccessary to do what you want.
Unfortunately, it doesn't run on Windows directly, although you can install for example a Linux virtual machine using Hyper-V on a Windows Server in order to run this on existing hardware.
Another alternative is simply to split the special devices off on a different VLAN. If you have managed switches, many models can automatically assign ports to VLANs depending on the MAC addresses of the clients. This feature may be called "Voice VLAN" on some models. This would of course not meet the "same subnet" requirement of your question, but you can always just get routing going between the two subnets.