The holoride retrofit itself does not require a phone. You might however still need one to play with holoride.
The holoride retrofit does not require a phone to function correctly. It receives location data from the global navigation satellite system (GNSS) which it passes along to the holoride App. The holoride App runs on your VR headset and requires an internet connection.
This internet connection could be provided via your smartphone. Since the internet connection is generally only used for localization purposes it will not use up too much of your mobile data volume. Depending on the distance travelled while playing we do not expect the used bandwidth to exceed a few MBs per hour.