Add mem_usage values to your xively.com stream from cron

xively_mem_usage.sh

#!/bin/bash
curl --request PUT \
  "https://api.xively.com/v2/feeds/FEED_ID_GOES_HERE.json" \
  --data '{"version":"1.0.0","datastreams":[{"id":"mem_usage","current_value":"'$((`grep MemTotal /proc/meminfo | awk '{print $2}'`-`grep MemFree /proc/meminfo | awk '{print $2}'`))'"}]}' \
  --header "X-ApiKey: API_KEY_GOES_HERE"

xively_mem_usage_expanded.sh

#!/bin/bash
MEM_TOTAL=`grep MemTotal /proc/meminfo | awk '{print $2}'`
MEM_FREE=`grep MemFree /proc/meminfo | awk '{print $2}'`
CURRENT_VALUE=$(($MEM_TOTAL - $MEM_FREE))
curl --request PUT \
  "https://api.xively.com/v2/feeds/FEED_ID_GOES_HERE.json" \
  --data '{"version":"1.0.0","datastreams":[{"id":"mem_usage","current_value":"'$CURRENT_VALUE'"}]}' \
  --header "X-ApiKey: API_KEY_GOES_HERE"