Having a working light client implementation is critical for bringing Ethereum to mobile, wearable, IoT and embedded devices. There is already an Android port of ethereumj (see it running on Samsung Galaxy S6 and inwatchZ). That client code can either run as a full-node or in a mode where the Android client communicates with a full node over json-rpc.
Full nodes are probably too heavy-weight to be practical for smartphones, let alone for smaller devices. Jarrad Hope and co are going to be looking at a full light client implementation for ethereumj too. We are collaborating on Gitter, now working directly with the go-ethereum team.
Initial targets for the go and C++ Ethereum light clients are likely to be some of the following devices:
- Single Board Computer / IoC
- Light Client Protocol wiki page
- Generalized Merkle DHT wiki page
- Ethereum ÐΞVcon-0: The Path to the Ethereum Light Client video
- Ethereum Wire Protocol wiki page
- Trie Usage section of the Design Rationale wiki page.
- RLPx: Cryptographic Network & Transport Protocol markdown document.
- State Tree Pruning blog by Vitalik, 26th June 2015
- Light Clients and Proof of Stake blog by Vitalik, 10th January 2015