The Disneyland Resort has now launched a service which allows Guests with web-enabled devices to purchase and receive tickets through them. At this time, however, the resort is allowing only 1 day tickets to be purchased this way (both single and park hopper options available).
In order to purchase a ticket this way, point your mobile browser to DisneylandMobileTickets.com and fill out the secure order form. Once the order has been processed, you will receive your ticket in the form of a bar code on screen as well as by email. Cast members at the turnstiles will then be able to scan in your ticket bar code and allow admission.
According to the site, each transaction may be for up to a total of fifteen tickets and they must be used prior to December 31, 2013.
Please note that to our knowledge the Disneyland Resort has not yet officially announced this service, so until they do, using it is at your own risk.
UPDATE #1: 6/8/12 – This option has now officially been confirmed by the Disney Parks blog.