How are indoor applications programmed?

Question

iOS

Hello. Tell me, how are indoor applications built? It is clear that using iBeacon, but how exactly are maps drawn? How are movements programmed?
I found several SDK
meridianapps.com
www.insiteo.com
and the like, but they are paid, but I would like to do it myself and for free. I found info that they draw on Cocos, but I would like to hear info from people who have come across a similar one. What is the best way to proceed? How to draw? How to stretch then? Maybe you should use Unity at all?