For the Scenario which you are asking at the server side "Blaze Ds" should be used.But as you are having the php at the back end so I will prefer you to keep hitting a httpService or web service by the second application(by using the timer with small interval) and get the result on a specific time interval.When the return result is different then the previous one then just use that data to populate in you grid.
Then, the time interval should be implemented in both applications since the first one inserts data and the second one delete the data. Instead of doing time interval I eliminate the second app and make 'states' in the first app for the 'add' and 'delete' data so I was able to open two instances of the app, one using the add state and the other with the delete state thinking that since was the same application both update at the same time but unfortunately I was wrong and one needs the browser refresh anyway. I really not know how to do time interval in flex since is different to flash that you just do the interval for the next frame and back to the first to load the data since is a timeline based app, flex not, besides, I'm just start using flex a couple weeks ago and don't know much about the coding but I will keep researching to do that. Thanks for the advice and sorry to take so long to answer.