History compare

In order to quickly see what has just happened on the network, it would help to have a "previous reading" memory. For example, I have just done a network scan, then I turned on a new machine, of which I do not know the IP address, by doing a second reading, but keeping the first list online, I can easily find my item. The same way for a element that has gone offline, a second reading will make it evident.
This would be an enormous help for medium size network admin, saving hours in looking for IP's and machines.
Another example. I have a machine of which I do not now the IP address. I do a first reading with it on, then turn it off, and do a second reading. There you are, the IP just gone off is my guy !
This can be obtained by showing the two readings side by side, or by simply flagging any changes from the previous reading.
Thanks, Giorgio