Off the top of my head, here are a couple of risks:
1) you don't have a quality control over the parts, yet you have to accept back any faulty units. That means you need a good working relationship with the OEM, in terms of being able to return kit.
2) the customer abusing the system/bike - accidentally or otherwise. Many people don't take care of their bikes. Educating them will be part of your costs in terms of time (as opposed to building stuff). This can be offset by offering reasonably priced servicing to make sure they keep working, and guarantees you some ongoing income.