  Due to increasing sensing capacity, smartphones offer unprecedented
opportunity to monitor human health. Affect sensing is one such essential
monitoring that can be achieved on smartphones. Information about affect can be
useful for many modern applications. In particular, it can be potentially used
for understanding cognitive decline in aging population. In this paper we
present an overview of the existing literature that offer affect sensing on
smartphone platform. Most importantly, we present the challenges that need to
be addressed to make affect sensing on smartphone a reality.
