The wallet is the device. A wallet is nothing more than a user interface to an account on a blockchain, be it hardware or software. In the case of a hardware wallet like a Ledger, the private keys to access the wallet are stored in hardware and never leave the wallet. So it can be used to send bitcoin and ether securely from any computer that can access the blockchain, even if that computer is filled with viruses, spyware, and keyloggers. That's the benefit to a hardware wallet - your account can't be hacked because the wallet is incapable of exposing the private account keys that are required to initiate a transaction, by design.