IoT Platforms: Which Hardware?

For ease of use, I recommend boards with built-in WiFi or Bluetooth capability. Relying on a shield is possible, but is often more difficult to configure and more expensive to buy.

The links redirect to the reviews of the boards.

LaunchPad

• ​LaunchPad WiFi with CC3200, a clear winner for USD30
• Connected LaunchPad with Ethernet 
• BoosterPack CC3100 to plug into any other LaunchPads

​Both the CC3100 and CC3200 manage the IP stack as well as encryption in hardware. The Wiring/Arduino compatible Energia IDE offers full-support and features built-in libraries for Temboo and PubNub.

Other vendors offer similar boards based on the CC3200, like the RedBearLab.

Arduino and Genuino

• Arduino Yún 

The dual-processor board is easy to use and well documented, albeit difficult to understand, as each processor can control the other.

• Arduino Tian

The Arduino Tian is a more powerful version of the Arduino Yún, with dual WiFi and Bluetooth  connectivity, a more powerful MPU, and an updated Cortex-M0 MCU as in the Arduino Zero or M0 Pro.

• Geniuno Zero Pro + WiFi Shield 101

The Arduino compatibility comes with a hefty price, USD100, when competitors offer better integrated and more powerful solutions at a fraction of the cost.

MediaTek LinkIt 

• ​The MediaTek LinkIt One includes WiFi, Bluetooth, GSM/GPRS and GPS on a single board compatible with Arduino shields.

MediaTek offers a cloud service as well as an app for Android.

• ​The MediaTek LinkIt Smart 7688 Duo offers the same dual-core configuration as the Arduino Yún board, but at a fraction of the price.
  

The processor MT7688AN runs on Linux for WiFi and the ATmega32U4 controller is compatible with Arduino. 

Udon Neo

• The Udoo Neo combines a Cortex-A9 MPU with a Cortex-M4 MCU in a single SoC, with WiFi and Bluetooth. 

The Udoo Neo excels at its ease of use, as it brings on-the-fly upload and run for the MCU, contrary to similar MPU+MCU configurations difficult to operate. 

RedBear Duo

• The RedBear Duo board combines WiFi and Bluetooth (2.0 and BLE).

Other Boards

• LightBlue Bean with Bluetooth

A very nice BLE-based solution with a local server running on Node-RED.​

• chipKIT WiFire

A really powerful board, but the IP stack is managed by software.

• BLuno with Bluetooth and Wido with WiFi

• Particle Core and Particle Photon with WiFi

Maybe the pioneer of the WiFi-ready boards. Unfortunately, the lack of offline standard IDE limits their potential.

• ESP8266-based boards

​Ultra cheap at USD10~15, but with some technical challenges.