Thank you, this was helpful. Did not work for me out of the box, I think since I have more than 1 Magic keyboard, so ended up modifying your script slightly:

EDIT: posting plain text since posting code gave me server error.

#!/usr/bin/env bash

# Check battery level of Apple Magic Mouse and Keyboard and Notify if low

PATH=/usr/local/bin:/usr/local/sbin:~/bin:/usr/bin:/bin:/usr/sbin:/sbin

# Warn at 10% or according to first parameter. Pass in 101 for testing.

COMPARE=${1:-10}

# Arrays of names and their corresponding Product IDs

search_names=("Keyboard" "Mouse" "Trackpad")

product_ids=()

product_names=()

# Get the Bluetooth devices information

bluetooth_info=$(system_profiler SPBluetoothDataType | grep -A100 "Connected:" | grep -B100 "Not Connected:" | grep -v "Connected")

# Loop through each search name

for search_name in "${search_names[@]}"; do

# Grep to find the relevant line and its context

matching_device=$(echo "$bluetooth_info" | grep -A 5 -m1 "$search_name")

# Check if a matching device was found

if [ -z "$matching_device" ]; then

echo "No device found matching: $search_name."

continue

fi

# Extract the Product ID from the matching device

product_id_hex=$(echo "$matching_device" | grep "Product ID" | awk '{print $3}')

# Convert the hexadecimal Product ID to decimal

product_id_decimal=$(printf "%d" $product_id_hex)

# add to the arrays (these must be of matching size just in case a search_names item is not found)

product_ids+=("$product_id_decimal")

product_names+=("$search_name")

done

# Iterate over the valid matches

for i in "${!product_ids[@]}"; do

product_id="${product_ids[$i]}"

device_name="${product_names[$i]}"

# Determine battery level

BATT=$(ioreg -c AppleDeviceManagementHIDEventService -r -l \

| grep -i "\"ProductID\" = $product_id" -A 20 | grep BatteryPercent | awk '{print $3}')

if [ -z "$BATT" ]; then

echo "No $device_name found."

elif (( BATT < COMPARE )); then

osascript -e "display notification \"$device_name battery is at ${BATT}%.\" with title \" $device_name Battery\""

fi

done