Also, that application is $20 for the East and $20 for the West. Since most GPS units offer complete North America maps, it would equate about $20 (east) + $20 (west) + $20(? for canada) = $60.
I wouldn't get my hopes up for a Garmin application. Since they are hard at work on the NuviFone, I don't think they would take away potential sales of their hardware by providing software elsewhere. Although, I might be wrong since Amazon did it with Kindle.