Wifi Signal Measurement App Development - Android

I require an Android App to be developed that will run on a Samsung Galaxy Tab 7 or 8” or alike. This app will be designed for a productivity tool which will be used to monitor the user (or carrier of the device) when they leave and enter a designated area or workstation. Once the app or device enters or leaves the workstation the user will be prompted to enter a reason via the screen which will be in the form of 4 or 5 push buttons and/or a short comment via the “Other” selection and text box. The device will continually alarm until a user input is selected and completed. The method that will be used to detect if the operator leaves the area will be a formula that will use signal strength (dbm) from the router to the Android device. On research this can be done successfully and it seems the only issue that causes inconstancy is interference like other transmitting devices or solid structures like walls etc. This will be used in an open factory were interference should be minimal. I’m hoping the detectable range can be as low as 10 meters from the router, therefore detecting if within or outside of the 10m radius give or take a couple of meters. The user input information that is selected to be appended to a SQL backend or as an alternative can be tabulated and sent in spreadsheet format (or alike) and sent via email automatically, this will be discussed and decided with successful freelancer. Further details will be discussed with successful freelancer, I am open to other methods or suggestions to better achieve what is require if the developer wishes to discuss. Happy freelancing :-)