Settled State DS

So i have, at least what i think to be an interesting problem. Wondering if you have solved this a different way maybe, of if there is a solution you know of, or maybe just thoughts on how you would approach/implement this.

So i have a dataset that is prone to sudden bursts of change, lets say value of A over the course of 10 seconds changes 10 times. The interim states of A are not important to me, but a settled state of A especially in case of the change of A is important. So i am looking for a datastructure that will keep data in a key-value pair, and allow it to change rapidly, but then as some time passes (perhaps a minute, or a few minutes), i need to know that A has entered a settled state, and then act on it.

It feels sort of like memcache, with the only difference that when memcache times out data, it simply removed data from the data set, so that next time you request it, it simply returns nothing, but it doesnt trigger any action when data times out, and it also just nulls the data.