I tried your Estimote App and saw that iBeacon detection is very instable.
I then tried the Airport tuto App and saw it doesn’t work at all!!!
Test was made on one Nexus 7 2013 Wifi and one Nexus 7 2013 LTE with the same result!
I then test Airport App on Galaxy S4 and here it perfectly works.
So do you guess what’s wrong with Nexus 7??