I did the same about mid 2015 using yowsup (Python API to Whatsapp). But it's was a private project because of legality concerns of hoarding so much data.
I tried to do something like that over 2 years ago. I never got to work on the analyze part of the data. I still have a 2GB database of online/offline, status (text status thingy) and profile picture changes. Someday I'll get back to that data and analyze it.
I don't see why people suddenly panic about it.. That's not a new thing. I wrote my own Tracking app over 2 years ago. I still have the code and database laying around.
I was using https://github.com/tgalal/yowsup back then.
Back then you could even see when people requested your online-status. Meaning you could see when they opened your chat. Back then I used that to see if my message have been read because the message-read notification didn't exist back then.