No need for any wifi trick, GPS drifting, or any other 3rd party device. Just walk around in house with your phone in your pocket.
Adventure Sync when paired with Google Fit will track the number of steps you take, that means even walking around the house, you will be able to get a surprising amount of steps and distance. This is not only legitimate but rewarding especially if you stuff in the house like vacuuming or gardening or whatever.
Another option on top of this, if you really don't want to walk at all is to rock your phone (shake your phone around an approximate walking pace). This is similar to if you were just on a treadmill in the house so it is still technically legit steps.