Here’s a very interesting post about capacitive touch interfaces.
Capacitive touch sensing is a popular alternative to mechanical switches and knobs in consumer electronics […]. In traditional designs, capacitive touch sensing is implemented by using a dedicated IC, while advanced user interface features such as proximity sensing, LED dimming, haptics, and liquid level detection are implemented with one or more separate ICs. Using multiple ICs increases board size, BOM cost, and time-to-market. In this article we discuss how to design advanced user interfaces using a single SoC.