Virtual Boltcard

This app uses Android HCE to emulate Boltcards. But only the POS-communication part. Configuring Boltcards using NFC is not supported.

How it works

if you start the app you have have to authenticate with your fingerprint or device-pin this is because you have access to a lnbits wallet once the app is started. Also you can change the active card.
with no card configured, you have 3 options to start:

create a lnbits account - creates an account, boltcard and lnurlp link on specified lbits-server. You can specify serverurl name and limits or just go with the defaults, currently legend.lnbits.com The app saves the apikey and tracks the balance of your account. the qrcode for the paylink is shown. if you tap it a installed wallet that can handle lnurlp should open. currently there is no export of the cards, so make sure if you setup a new LNBits-card to open the wallet and backup as usual
import an existing boltcard from an lnbits wallet. Qrcode or url accepted.
manually setup an existing boltcard

you can setup multiple cards (the "+"-bubble in the lower right of the screen is the only options currently.)
active card is always the visual card. Just swipe another card in view to activate it.
there is currently no way to disable emulation, so you have to deactivate nfc to do that atm.
emulation currently also works from the lockscreen. it stops if the screen is black, but once its on hce works and we are not quiet sure yet if thats a good or a bad thing.

The app stores your boltcard url, keys and counter in encrypted settings-storage and an encrypted mssql database the password is randomly created on the first launch and saved to the encrypted settings-storage.
Everyone with access to this data is able to access your sats.
If you create an lnbits wallet from within the app, the api-keys are saved as well in the encrypted mssql database.
I tried to get this reasonably safe, but i am not an experienced app-developer so i probably have completely missed that. In that case please leave an issue so we can fix it :-)
a Boltcard is a offline device which keeps the cards url, keys and counter. You decrease security by putting this data directly onto your phone.