We would love to record indoor movement, but our app's algorithm is not able to verify movement taken indoors... yet. There is a lot of work underway to develop the functionality to do this, but it will take some time.
The app's algorithm removes steps that are not likely directly from exercise to eliminate the possibility of cheating and GPS helps us do this at the moment. After all the value of Sweatcoin will depend on our ability to ensure that every Sweatcoin that goes into circulation is earned by someone's sweat.