What I have done is use the remote probe software on inexpensive netbooks. We have placed them in the field with static IP addresses assigned by our DHCP server. We have assigned really short lease times to these Static entries. This way you get a probe on the network you want to query you DHCP server on. This really works well in our environment as we have lots of subnets and we relay DHCP through our layer 3 routers. If the probe goes down and the network gear still appears to be up we start looking. This does not solve the problem of trying to determine if you have a rogue DHCP server on your network as a static address would be a more detailed response then your average wireless access point or home router might send out. DHCP clients tend to prefer the response from the DHCP server that provided the most detailed information first.
I'd add this setup with netbooks also allows us to do some QOS mesh testing when needed too.