This guide is for installing the Ethereum PyEthApp client on a Raspberry Pi 2. Parameters are available for storing blockchain data on a microSD card or on an external USB device. EthDev supports three Ethereum clients: Eth (written in C++), Pyeth (written in Python), and Geth (written in Go). This tutorial is designed to install PyEthApp, just to start creating the Pyeth client. Ethereum is an extremely new technology and is in rapid development, so expect a bumpy ride and some challenges if you start at this point. If you run into any Raspberry Pi issues by going through these steps, then the Raspberry Pi Docs are a good source of help.