I haven't looked into much of the GMail push stuff as I am not that urgently needing mails, and don't use any push stuff, so am not 100% sure of all the options.
I do know there is a lot of mention online of Boxcar which can do push for a whole load of services, 1 free in app (you pick which) then in app purchases if you want others. Fro more info etc. and a review of that it can do check this article
There are probably plenty of other options out there too.
Aaah, so push mail is where the mail server lets the client know that mail is available, instead of the mail client continuously asking the server if it has mail.