Buying a kit isn't everyone's cup of tea. In fact, we see the eChook kit as a first stepping stone to instrumenting a car and hope teams will be able to move on to custom designs to satisfy their needs.
Everything we have created except for the telemetry is open source. This means you can use as much or as little of it as you want in your designs.
If you have PCB etching facilities then designing your own PCB, potentially reusing the eChook circuit schematics, or if you have an existing data logging board, you may be able to connect a bluetooth module and be able to use the eChook app and telemetry. See the Bluetooth Communication section for more details.
For insurance reasons (ugh) we can't give you modifications to make to the eChook if you have bought one of the kits, but we are always happy to answer electronics questions - pop over to the forum or Slack channel.