Read AirTag data from the FindMy.app cache and convert to GPX

airtag-to-gpx-sync.sh

#!/usr/bin/env bash

# 
# Reads AirTag data from the FindMy.app cache and converts it to a daily GPX file
#
# Rsyncs the data to a web accessible folder that can be displayed with e.g. 
# https://gist.github.com/henrik242/84ad80dd2170385fe819df1d40224cc4
#
# This should typically be run as a cron job
#

set -o pipefail -o nounset -o errexit

export PATH=/usr/local/bin:$PATH
DATADIR=/tmp/airtag-data
TODAY=$(date +%d)

mkdir -p $DATADIR
DATA=$DATADIR/airtagdata-$TODAY.txt
GPX=$DATADIR/airtagdata-$TODAY.gpx
TAGNAME=Foobar

if [[ $(uname -s) == "Darwin" ]]; then
  TOMORROW=$(date -v +1d +%d)
else
  TOMORROW=$(date --date="tomorrow" +%d)
fi
rm -f $DATADIR/airtagdata-$TOMORROW.gpx

jq -r '.[] | select(.name == "'$TAGNAME'") | .location | "\(.latitude) \(.longitude) \(.altitude) \(.timeStamp/1000 | todate)"' \
   $HOME/Library/Caches/com.apple.findmy.fmipcore/Items.data >> $DATA

START='<?xml version="1.0" encoding="UTF-8"?>
<gpx xmlns="http://www.topografix.com/GPX/1/1" xmlns:mytracks="http://mytracks.stichling.info/myTracksGPX/1/0" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" creator="myTracks" version="1.1" xsi:schemaLocation="http://www.topografix.com/GPX/1/1 http://www.topografix.com/GPX/1/1/gpx.xsd">
   <trk>
      <name>'$TAGNAME'</name>
      <extensions>
         <mytracks:color red="0.000000" green="0.000000" blue="1.000000" alpha="1.000000" />
         <mytracks:area showArea="no" areaDistance="0.000000" />
         <mytracks:directionArrows showDirectionArrows="yes" />
         <mytracks:sync syncPhotosOniPhone="no" />
         <mytracks:timezone offset="120" />
      </extensions>
      <trkseg>'

END='      </trkseg>
   </trk>
</gpx>'


echo $START > $GPX 

function elems() {
    LAT=$1
    LON=$2
    ELE=$3
    TS=$4
}

cat $DATA | while read line; do
  elems $line
  echo '<trkpt lat="'$LAT'" lon="'$LON'">
            <ele>'$ELE'</ele>
            <time>'$TS'</time>
         </trkpt>' >> $GPX
done

echo $END >> $GPX
cp $GPX $DATADIR/airtagdata.gpx

rsync -a --exclude='*.txt' $DATADIR example.com:public_html/airtag/

The best recommendation is to buy a cheap Mac that supports macOS Sonoma 14.3.1 (minimum models: MacBook Air 2018, MacBook Pro 2018, Mac mini 2018, iMac 2019, or newer).
Install macOS Sonoma 14.3.1, the last version before Apple started encrypting Find My cache files.
This allows you to read AirTag and shared item locations directly from:

~/Library/Caches/com.apple.findmy.fmipcore/Items.data
~/Library/Caches/com.apple.findmy.fmipcore/Devices.data

With this setup, you can still extract the data in plain format using available scripts.
In newer macOS versions, reading this data is practically impossible due to the encryption implemented by Apple.

The best recommendation is to buy a cheap Mac that supports macOS Sonoma 14.3.1 (minimum models: MacBook Air 2018, MacBook Pro 2018, Mac mini 2018, iMac 2019, or newer). Install macOS Sonoma 14.3.1, the last version before Apple started encrypting Find My cache files. This allows you to read AirTag and shared item locations directly from:

~/Library/Caches/com.apple.findmy.fmipcore/Items.data
~/Library/Caches/com.apple.findmy.fmipcore/Devices.data

With this setup, you can still extract the data in plain format using available scripts. In newer macOS versions, reading this data is practically impossible due to the encryption implemented by Apple.

I am using a Mac Mini 2012 with Sonoma 14.3.1 for my data collection along with a bunch of VMs running Monterey. Sonoma is better as it can access shared tags as well but Monterey is a good fall back since it can run in a small Macos VM under windows. With a 16 GB memory on a windows box you can run 5 VMs with no issues getting you 5 x 32 tags = 160 on 1 box!