More complicated clients, one which monitor updates from the steward looking for changing conditions, and reacting to them on behalf of the user by asking the steward to perform actions, are entirely possible. Technically speaking these are intelligent agents working in a multi-agent system with shared goals of making life more convenient for the user. We like to think that we're implementing magic.
Necleus is a smart lock based on IoT built on Arduino uno and Ethernet shield. It can be accessed by a key and internet through software interface built in java. He's used an I2C EEPROM as key which hardly costs 15 cents resulting in an inexpensive key.
The system consists of a low power consumption PC running Windows 7 (Dell OptiPlex FX170), an APC Rack PDU AP7940 to control the well pump, and an Arduino UNO R3 with a 3 wire 15 psi water pressure sensor and a Ethernet Shield.
The project is about to create a system for settlement by the Popcard in commercial vending machines.
The author is a vending machine in the hallway of their building and was selling drinks to your neighbors. Think of how selling drinks without cash, started this project.