I sometimes use the 'watch' command to monitor for instance a large filecopy job or download or whatever.
watch is a nice tool to do such things. It runs a command of your choice every few seconds and clears the terminalscreen in between and you can modify the value of those every-few-seconds (default 2 seconds) to whatever you like.
Now, I hate to run commands unnecessary ... might be OCD or whatever ... I just don't like wasting CPU time. 
With watch you have the to adjust the delay between screenupdates manually so you have to guess what interval is optimal.
That gave me an idea:
Why not setting the delay between commands automatically ?
Start with a 2 second delay between commands and if a screenoutput does not change just increase the delay until it does.
This is the result and it works like a charm. It works exactly the same as the regular watch command but it sets the interval automatically and lacks any options.
#!/bin/bash
# Initial delay value in seconds to wait between command runs
delay=2
# Maximum delay value in seconds to wait between command runs
max_delay=3600
while :
do
# Your command is executed here
output=$( eval "$*" )
# decide how long to wait until running command again
if [ "$output" = "$previous_output" ]
then
(( delay < max_delay )) && (( ++delay ))
else
clear ; echo "$output"
previous_output="$output"
fi
echo -ne "\rdelay between updates = $delay sec"
sleep "$delay"
done