GPS Tracker using Wifi

Ok, so right up front I'm going to say that this is only my second Aruino project and way more complicated than my first one (turning a light on and off). In an effort to avoid turning this into an XY Problem (http://xyproblem.info/), here is what I've got going on.

I recently had an expensive piece of equipment taken from our office. I eventually found it, but it was a lot of effort. This is something that I would like to avoid repeating.

I would like to build a device that goes in the box with my equipment and just stays there. Then based on some prearranged conditions (indicating that it has left the building) it should start to phone home.

I have very little experience with Arduino, so I would like to know if my plan makes sense before I go off and buy a bunch of stuff. I already have an Arduino Uno, so I don't need a new one. I've seen several tutorials that use GPS and some that use Wifi. It seems to me that I should be able to build a unit that I can place on my equipment. Then when it loses Wifi connection with my SSID (or is removed XX number of feet/miles from my office) it starts attempting to connect to public wifi. Then when it connects to a public wifi SSID it sends it's coordinates to me. I also looked at several GSM options, but it seems to me that all of them require you to put your phone SIM card in. I don't want to pay a monthly fee, if possible. I really don't care how I get there, but I want a device that tells me where my equipment is in real time.

I hope this all makes sense. Thanks in advance!!!

These days, how many "public wifis" are there that don't require a password or sign in sequence?

OP,

I don't know what country you are in. If you can get a prepaid 30USD SIM card with say a balance that expires in 1 year, then would you do the GSM? Sounds like xy problem after all ;)

GPS is not good. Indoors you will rarely get a good fix. Wifi is ok if you are sure the equipment will be removed from the vicinity of your office. I think detecting Wifi SSID is a decent way of saying they are removed but don't know how to tell where they are.

Can you disclose what type of equipment you are losing? There may be other ways to secure it.

liudr, thanks for the feedback. i hadn't thought of a prepaid card. that's not a bad idea. that's probably what i'll do. as far as the equipment, here is what i'm protecting:http://www.hexagonmetrology.us/products/portable-measuring-arms/romer-absolute-arm. for now i've just put them under lock and key in my office. who knows, sometimes the simple solutions are the best. i'll still probably try the Arduino solution. at this point i just want to see if i can do it and it wouldn't hurt to have the added protection.

A NodeMCU (~$7) can be programmed in Lua or C/C++ (via Arduino IDE) and has quite good, built-in WiFi. Couple that with an inexpensive GPS module and you'd be good to go.

Battery life would be a bit of a pain. Two AA batteries should keep it fed for over a month if the GPS is kept shut off; wait for the local WiFi network to disappear before activating the GPS, I guess. But long term it would still be a maintenance hassle.