Hi!
We have experience of building Android Apps with OpenCV through JNI. OpenCV code will be written in C++ to improve performance, and will be included in the project as a shared library.
One of the app we worked upon is similar. Java grabs the camera frames, sends it to openCV through JNI, OpenCV returns the modified frame and Java then shows it to the user. We have experience of implementing efficient algorithms to detect camera position based on the frames we receive using OpenCV.
We can build this app for you well within time and budget.