I needed the same functionality, and doing jailbreak is no-no. One solution is to host yourself DNS server (MaraDNS), go to your wifi settings in ipad/phone, and add your custom DNS server there.
The whole process took me only 10 minutes, and it works!
1) Download MaraDNS
2) Run mkSecretTxt.exe as administrator
3) Modify mararc file, mine is:
ipv4_bind_addresses = "put your public IP Here"
timestamp_type = 2
random_seed_file = "secret.txt"
csv2 = {}
csv2["Simple.Example.com."] = "example.configuration"
Add file called "example.configuration" into the same folder where run_maradns.bat is.
4) Edit your example.configuration file:
Simple.Example.com. 10.10.13.13 ~
5) Disable all Firewalls (convenience)
6) Run file "run_maradns.bat"
7) There should be no errors.
8) Add your DNS server to list, as shown here: http://www.iphonehacks.com/2014/08/change-dns-iphone-ipad.html
9) Works!