The missing part here is that something needs to tell the K2 Server that the value has changed. K2 does not do polling, rather, it waist for an external event that interacts with the K2 Server. One can do polling with K2, but it is almost never recommended.

Depending on the full requirements, there are a couple of options. But if you just want to send an email, you can create a generic process that gets fired every time the value in the column is updated. Have a look at the SharePoint Events Process wizard (Item Updated event), it should get you there, but you will still need to do some checking to see if the change was on the field in question. You will notice that a process with the mentioned process wizard creates an XML Field called EventDetails. In this field, there will be 2 sections, a Before and an After. Comparing the relevant field in these two nodes should tell you whether to proceed or not.

By the way how to check a particular column value before is not equal to the value after using the two nodes in the XML Fields as the only fields showing under before and after are "Title and Type"

Many Thanks

ID

Is there any updated answers on how to check a column in the list and tell the workflow what to do based on that?

I was able to pull this off using a line rule. First, you need an activity with an event that will sync the values. In my case, I used a smart object event to update process data fields against my SharePoint list smart object SmartObject. You should be able to draw the line to another activity, and then resituate the line to point to it's own source event. In the line rules you can check for the values desired. 

To keep it from looping every second, try adding a Start Rule to delay the activity.