Oh, ObjectDetect currently only supports modes with video output. But check out the tutorial by dbddv01 nevertheless, it is great!
To allow ObjectDetect to run without USB video output, we need to create an additional process(inframe) function in the module, which only takes an input frame in and sends no output frame. The code will be very similar to the one in the existing process(inframe, outframe) function, just strip out anything related to creating the output image.
If you are not familiar with C++, we can add this as part of a future release or tutorial.