Cool.. you are right down the street from me. I live in Shoreline, but I'm about 2 minutes from the intersection of Greenwood and 145th, which you probably live 2 blocks from
That entire stretch of 99/Greenwood is sort of the crest of a hill, so I think we have a lot of cell towers in the area.
I could be wrong, this one is $2.99 though..
http://itunes.apple.com/us/app/motionx-gps/id299949744?mt=8
I swear there was a 99 cent one.. I use my in-car nav so I'm no expert on the topic. Spend a little more for Tom-Tom has always been what I've heard though.