Have a look at Satodime (https://satodime.io). It is similar to openDime, but with a smartcard form factor.
Since it has NFC connectivity, you can use it easily on a smartphone by tapping it to the back of the phone!
Currently there is an app for android, the iOS app will be released in a few weeks.

The code running on the card is open-source and available here: https://github.com/Toporin/Satodime-Applet
Bonus: the card can store up to 3 vaults, and each slot is reusable!