This has already been posted on the Southwest forum, but it really is good news for all frequent flyers - we should be pushing all the major airlines to provide news like this.

According to the Southwest Web site - this appears to have just been posted December 30 - you can print a "Security Document" to present to the TSA screeners in lieu of a boarding pass. I haven't seen a "Security Document", so I don't know exactly what's on it, but all airlines ought to provide something similar - perhaps start printing bar codes on the e-ticket receipts?

Gate check-in lives! (I think) Contact your airline today!