Ha, I built exactly this, but just the outbound part because I use a single Google Apps account with a wildcard address and routing rules to handle all the inbound mail. I even considered wrapping it up as a service like this, but decided against it because I'd want to be able to give every customer a dedicated IP (as to not affect other customers if they misbehave) with a clean mail reputation that has been confirmed working and/or cleared with major mail providers, which simply introduces too much overhead for a reasonable price point. Allowing multiple customers to send mail from the same IP seemed too risky.
Anyway, this looks pretty well done though and I like the name/domain.
PS: under "advanced routing" on the home page, it says "Your domain's address space is easily tames with Gmailify's routing" ... I think "tames" was meant to be "tamed" :)