The official eMark website currently offers core wallets (eMark-qt) for the most common operating systems for downloading to your own PC or MAC.
For example, an online wallet for eMark is offered on emark.space (not official eMark site). It requires a registration.
It's a wallet in the form of an app for downloading and using on the smartphone/tablet. Currently (February 2018) an Android wallet is under development for the eMark. An eMark wallet for IOS will follow.
The transaction key is printed on it and physically stored together with another private key that unlocks the transaction key. (for example, vault, etc.) On eMark Website you can create and print your own eMark paper-wallet.
Special storage medium, usually in the form of a USB stick or chip, on which the transaction keys are also stored physically/offline (so-called "cold storage") and can be protected against unauthorized access by additional passwords. According to the overwhelming majority of experts, this is currently the safest form of storage. Unfortunately, no manufacturer currently offers an eMark compatible hardware wallet.