Actually, it *is* designed for people who can barely get off the couch! It builds up your stamina in small increments, and you can stay at any stage as long as you need to and of course go at a pace that is sustainable to you. It's a really great program.
I used MapMyRun and it kept me motivated by drawing a map of my route, keeping time, pace, etc. It would post to facebook which also help a lot with motivation because friends or other mapmyrun users would post encouraging things.
C25K gives you more structure to follow if you need that, and mapmyrun type apps leave the structuring to you.
I also used a fitbit which had a ton of motivating features.