How much coding work would go into a program that deciphered the location and direction of a cell phone and could represent up to 20 cell phones on one map screen?

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tablet

I'm looking to employ someone (or figure out myself) to code a device that will allow me to track the location and orientation of up to 20 people at one time using an app on a tablet. The type of tablet is still up in the air, and the hardware that goes into the system is also in question.

In addition to the above information, the coding would also have to decipher other information sent from each of the tracked personnel. This information consists of unchanging variables such as hair color, height, blood type, and also ever-changing variables that would need to be updated by the tracked personnel.

[Edit: Removed the email address, we can use this forum to contact you. Exposing your email address like that can open you up to spam ;-)]