Internet of Things
Internet of Things is a category of consumer electronics that emphasizes very small form factor, extremely low power consumption, and frequent, bite-size data reporting. Often these devices are collecting information without direct user intervention so need to use sensors that measure ambient condition changes. Bluetooth, BLE, or wifi for communication can be used depending on overall system requirements.
I've created many IoT projects for clients for home use, for entertainment and for personal data collection.
When a small number of prototypes are needed quickly, as required for user studies, for example, combining off the shelf components and small specialized custom sensor board is often the best approach. This allows quick kickstart of the firmware and reduces testing overhead.