This is the source code of the resolver.00f.net service.

It responds to DNS queries with the client (resolver) IP address.

$ dig +short resolver.dnscrypt.info
74.125.181.207

-> Aww crap, this VPN service is actually sending DNS queries to Google.

$ go get github.com/jedisct1/whatsmyresolver
# myresolver -listen <myresolver ip address>:53

And delegate a zone to this IP:

resolver.example.com. IN NS resolver-ns.example.com.
resolver-ns.example.com IN A <myresolver ip address>