A Digi-Token™ is any cryptographic USB token that has been tested and approved to work with Digi-CA™ [3]. And because most modern computers have a USB port, USB tokens are probably the most convenient hardware for storing a user's digital certificate/signature.
Links:
[1] https://www.digi-sign.com/digi-card
[2] https://www.digi-sign.com/digi-token
[3] https://www.digi-sign.com/digi-ca
[4] https://www.digi-sign.com/hsm