In addition to well known Raspberry-pi and arduino following are some lesser known but cheaper device for DIY hacks:
- ESP8266 (WiFi)
Cheap WiFi module providing b/g/n connectivity using few AT commands over UART interface. It costs less than $3.5 (less than INR 300 in India). Manufactured by Espressif, which also provides IoT SDK. Also this module is currently supported in Arduino IDE as well.
- nrf51822 (Bluetooth Smart)
The nRF51822 is a powerful, highly flexible multiprotocol SoC ideally suited for Bluetooth® Smart (previously called Bluetooth low energy) and 2.4GHz ultra low-power wireless applications. The nRF51822 is built around a 32-bit ARM® Cortex™ M0 CPU with 256kB/128kB flash + 32kB/16kB RAM.