there is now a free limited version of the app Bike Notes called Bike Notes Free available on App Store.
This is an app I made to keep track of the maintenance I do on my bike, hopefully someday bikes. I am not a professional developer, just a biker who borrowed a mac from my employer to try to do this app.
Current full version allows the user to set up eight service categories with different names and service intervals for each bike. Then when you do something to your bike you define a service with a status (miles/km/hours) on your bike and a comment under one of the eight service categories and that is stored on the phone along with the date that service was logged.
You can also store other info on the bike like license number, insurance or whatever you want.
You can then view what service is next and get a list of all the services you have done on your bike.
The free version has a limit of one bike and two service categories and only stores the last two services in each category. The bike info can not be saved in that version as well as editing the service category names or intervals.
if you have ideas on how to improve it you can post it on my facebook site facebook.com/bike.note
the free version is here
and the full version is here
Check it out.