gprs/gps bracelet

[Guilty_Crown]

Hello, I want to make a gprs/gps tracking bracelet for old people/kids/pets/etc....yes despite them being available in the market at reasonable prices -_-

anyway, the idea is that the gps tracking device will have two states, IDLE when it receiving a signal from a control unit that is located at the center of the range we want our user within, and ACTIVE when the user gets outside the range thus the signal received/transmitted is cut
when it's in ACTIVE mode, the control unit will send an alarm msg (email, sms, w/e) to the monitoring adult and from there said adult should be able to track the user through a dedicated server, signal, or however it's done

an extra feature I was hoping I'd have time to add is heart monitoring, which sets same alarm and activates the gps when necessary..however I believe it's only my wishful thinking..

So, what I needed is to know what pieces I'll need to achieve this (types of ICs, energy sources, type of GPRS/GPS chip and terminals) and what possible programming knowledge will I be needing..

thanks in advance to whoever can help and I'm open to other suggestions or guiding

 

[(*steve*)]

If it uses a GPS, then there's little point in having the perimeter determined by a received signal. It's far better to have either an allowed polygon or a point and distance to compare the current location against.

For this task you probably need to sample the location several times as GPS occasionally reports the wrong location due to multipath reflections, etc. Either that or the wearer needs to have been outside the boundary for some minimum time (say a minute).

In most cases your distance from the poles should be large enough that you can use lat/long as effectively Cartesian coordinates (perhaps with some scale fudging) over the very small range of values you would typically be using.