https://www.kickstarter.com/projects/1991736672/redbear-duo-a-small-and-powerful-wi-fi-ble-iot-boa
this looks like the ideal candidate for BLE presence detector: It has Wifi + BLE that can run at the same time and is ~$20. (5 for $100 incl shipping)
supports arduino sketch language.
I ordered 5
Karl