Step on it - I missed your post from a few weeks ago. I won't suggest what you should do, but I'll let you know that I conceived of this App after looking to get a new tripmaster and thought for my use that something more convenient, versatile and with bigger numbers would be better and safer for ME. I'm really pleased with the way it works.
One other thought. I've been using electronic odo devices since their dawn in the Enduro world many years ago. I seems that no matter how well the pickup and cable is protected that people continue to get failures...hence the reason many (most?) serious rally people run a redundant odo system. For amateurs, the iphone app at the least might provide a nice backup in case your official system goes bonkers. At the Baja Rally I needed a backup system and it was nice to have the iphone to fall back to. On day one I helped guide two riders who's ICO's had gone kaput and they had no backup...