We renamed your request slightly to match the feature name that it would correspond to. What you want is to say “execute Activity X on the locked iPhone in my pocket when it gets within 4m of this iBeacon”. What you’re suggesting would work in principle today if your phone was open and unlocked and you set the Estimote to a Minor value representing a known iOS device. But the key there to make it useful is to run it in the background when the phone is locked.
It’s something we’re planning to look at. It requires a lot more infrastructure and Apple approvals for running things in the background, etc. Assuming it can be done, which we think it can. Just a matter of prioritization.