This is the most wrong comment I've seen on HN in a long time. The SLAM in Hololens is incredibly impressive and nothing on any smartphone is one hundredth as good, with the possible exception of the still unreleased Project Tango phone.
"This is the most wrong comment I've seen on HN in a long time. The SLAM in smartphones are the same as the one in Hololens. Project Tango should prove even more impressive."
And no one would be any wiser.
Most smartphones simply don't have to do this, they don't have to map their environments without user input. They don't have to localise themselves within a map of the environment that they've built themselves. Project Tango does do AR and environment mapping on a smartphone, so it does deal with the SLAM problem too.