On 2018-01-10 the following merge request was submitted on the official development repository for Monero:
The goal of this PR is to propose code modifications to integrate the ledger HW into monero-wallet-cli. This code mod is not ready to merge (see below) but it is time to ask to the dev team and tech guys a first review for opinion.
The Ledger Wallet is a hardware wallet supplier that provides wallets capable of interfacing with many cryptocurrencies and digital assets. Presently, there is no support for Monero but their development team has entered the beginning stages of producing a codebase. The software application to be run on the hardware wallet can be found in the Ledger repository.