The logo MUST be square (or fit within a square box e.g. hexagon) OR it MUST have a major element that is square so it can be used for mobile application icon, favicon, etc.
The logo MUST be vector based and therefore able to scale as needed and be identifiable at different sizes.
These are just some ideas that come to mind. They are not requirements.
Something that includes location marker:
The app is collecting the current position when completing checks so it is location aware.
A check mark or tick might be too obvious unless it has been incorporated in a novel way.
As it is collecting defect data it is promoting safe transport
The checks are mandatory each day so completing them gives validation that the vehicle is safe to drive on the road.
The app collects data from multiple mobile handsets and sends it back to the web application.
The check data is collected on a mobile device.
Something that would appeal to a lorry/truck driver tapping every day to use the app. At the same time something that appeals to business decision makers as they will ultimately be paying for the software and using the website daily.
As the app may be used by a range of technical abilities I would like the logo to immediately identify what it does. Ideally it would be fun and playful.