What are some alternatives?
When comparing zzzz.io and FreeDNS, you can also consider the following products
Dyn - Managed DNS, Outsourced DNS & Anycast DNS
No-IP - Dynamic DNS and Managed DNS Provider
Dynu Dynamic DNS - Free dynamic DNS service with powerful features
Duck DNS - Free dynamic DNS hosted on Amazon VPC
ClouDNS.net - Free DNS, Cloud DNS, Managed DNS, GeoDNS and DDoS Protected DNS hosting with included web redirects, mail forwards and Round-Robin load balancing. Instant updates in Europe, North and South America, Asia and Australia.
nsupdate.info - nsupdate.info is a dynamic dns service.