My experience has been from the 21 to the front seat of my Sequoia. We each have Apple 6+ phones and the reception is similar and consistent. If I want to check temperatures while inside the house, with the trailer immediately adjacent, I have to move to the room closest to the trailer. In other words the 30 feet seems to apply.
While in the car the Accurite system would work occasionally from the middle seat, never from the front. Sensor Push claims to be using a newer version of Bluetooth technology, resulting in increased range. When I bought the unit in April there were 14 reviews on Amazon, it is now up to 70+. I have not read these recent ones but based on scoring it seems pretty good.
The issue will always be the number of uncontrolled variables: your phone, distance from the sensor, and interference (walls).
Paul and Janet Braun
2003 Toyota 4Runner V8 now 2012 Toyota Sequoia V8
Escape 19' 2010 now 2014 Escape 21'