Dear Madam or Sir,
I am an experienced C/C++ for (Linux), Python, and bash programmer. Therefore, this task can be done easily in a few days, hence my low price.
I would create a script that captures the network with tcpdump (in monitor mode?), save it every 12 hours, and make it avaiable with a http server on the wireless network (in station mode or access port node?) or uploade it to a server if internet connection is available.
To make sure that everything runs smoothely, programs are restarted when they crash, and the actions are scheduled I would use bash scripts, python scripts, cron and upstart which is integrated in Ubuntu/Picuntu.
You will get scripts that install and configure everything automatically.
I am looking forward to discuss the details in the chat.