[OT] dnsreport.com and utilities "behind" it?!?

[Netfortius]

Does anybody know what is dnsreport.com using to go over all the checkups 
(i.e. dig, host, nslookup, other utility), when queried for a specific domain 
"health"? I am trying to script some checkups to be run in cron, then email 
me results, from a remote site, so that I can make sure that my client's name 
servers stay healthy, or that they behave properly after changes. Some things 
are obvious (e.g. mail server query, then attempt for connection, or NS 
records at parent, etc.), while others are somehow obscure (e.g. WARNING: 
Your nameservers report somewhat different answers (what are those?!?) for 
your NS records (varying TTL, for example ... OK - what others, though, if 
the TTLs are OK?!?) --> what utility and what parameters are being passed to 
it, to obtain the results they are providing in such an example?!?). 

TIA,
Stef