Given that the only detail provided was to complete an Android application implementing its requirements that involves OpenCV, It is hard to come up with a more accurate proposal.
I propose a three steps development.
1. Gathering requirements, and make sure they are reasonable to the proposed bid.
2. Deliver a beta (prototype) version for each requirement:
- These prototypes are tested on the final application by the client, gather feedbacks and possible improvements
3. Deliver Final version:
- Implement as much as possible the suggestion from the feedback given by the client from step 2.