Easy, Cheap Locator Beacon <$5

Simple general use plug and play locator beacon for lost R/C model, transmitter hunting, etc... I know it looks odd because I used an old empty medicine container as a water resistant project box to encase the beacon.

The video shows a demo of how to locate the beacon, and also the circuit diagram. It's pretty self explanatory.

In case you are on mobile and cannot see the video embedded: Video

You can buy a ESP-201 on sites such as eBay.com, Gearbest.com, or Aliexpress.com. The shipping can take up to 40 days. Consider using PayPal to stay slightly more secure.

I just used an old toy quadcopter battery and spliced jumper wires from eBay, but you can buy these on the sites I mentioned in the last step, or salvage them.

Follow the wiring diagram and assembly photos from the video!

The wiring is fairly simple, the ESP-201 pins GPIO15 and any GND pin both go to battery negative (ground wire), and any of the 3.3V pins and the CH_PD aka CHIP_EN pin both go to the battery positive wire.

Then just snap the external antenna on.

Wrap a can such as a Pringles can or in my case a corn meal can with aluminum foil using tape. Make sure your phone fits in it snugly.

If you want to try something to maybe, theoretically speaking, increase range significantly, a cheap USB OTG Host Power Splitter like this one: USB OTG SPLITTER and USB power pack like this one: USB POWER BANK, you might be able to use an external WiFi antenna like this one: USB WIFI ANTENNA to locate the beacon from 3 kilometers away or so. I know that the OTG splitter + USB power bank + USB WiFi antenna + Android phone setup does not work with Motorola phones because of driver issues, and the app may not be compatible either, but you could try it if you want. I saw on YouTube a USB WiFi antenna working with the Nexus 5 1st gen. The purpose of the USB power bank is to supply power to the USB Antenna, because the phone cannot supply that much current.

Android signal meter app with audio Geiger counter style feature: WiFi Analyzer app by Farproc on Google Play.

This app is still in beta and buggy now (10/23/15), but it would work instead of using a foil wrapped can, but with reduced range: WiFi Radar app by Paul Girsas on Google Play