Google started to roll out IMAP access on some accounts in Gmail.
So far, one of my three Gmail accounts has had it enabled.  I set it up with my computer and iPhone.  Now when I get email and read it, move it, or delete it, in one place, it does the same for the other device since the mail is stored on the server and is synchronized using IMAP.
You can find out more about Gmail IMAP here.