I run DNSimple (https://dnsimple.com) and we have a full REST API and support domain registrations, transfers and SSL certificates as well. Plus we have an ALIAS record type that's very useful for pointing your apex to services where they only provide a hostname.
I'll be happy to answer any questions you have regarding our service either here or through our support channels.
I'll be happy to answer any questions you have regarding our service either here or through our support channels.