  With advancements in technology, personal computing devices are better
adapted for and further integrated into people's lives and homes. The
integration of technology into society also results in an increasing desire to
control who and what has access to sensitive information, especially for
vulnerable people including children and the elderly. With blockchain coming in
to the picture as a technology that can revolutionise the world, it is now
possible to have an immutable audit trail of locational data over time. By
controlling the process through inexpensive equipment in the home, it is
possible to control whom has access to such personal data. This paper presents
a blockchain based family security system for tracking the location of
consenting family members' smart phones. The locations of the family members'
smart phones are logged and stored in a private blockchain which can be
accessed through a node installed in the family home on a computer. The data
for the whereabouts of family members stays within the family unit and does not
go to any third party. The system is implemented in a small scale (one miner
and two other nodes) and the technical feasibility is discussed along with the
limitations of the system. Further research will cover the integration of the
system into a smart home environment, and ethical implementations of tracking,
especially of vulnerable people, using the immutability of blockchain.
