Did you know that you can “watch” your bitcoin TREZOR wallets with the use of Mycelium?

Why is this useful? Maybe you want to keep track of your account balances, without the need to carry your TREZOR everywhere and plugging it into a computer. Or alternatively, maybe you want to be able to receive transactions directly to your TREZOR wallets, through a QR code on your phone. The choice is yours, we give you the feature!

To use this feature, you will need an Android phone with USB-host support, an OTG cable, and of course, your TREZOR device. (Don’t have an OTG cable? Scroll to the end of the article.)

How does this work?

In Mycelium, you can import TREZOR as another Account into the application. Mycelium imports only the XPUB of your selected TREZOR account, which allows the app to see the your account balance even without the device being plugged in. However, Mycelium never gets access to your private keys! If you decide to spend bitcoins from your TREZOR, you will still need to plug your TREZOR into the phone or a computer.

Import as an account

The process is straightforward, you may follow our guide here to make it easier. Steps are marked by red rectangles.

Plug in your TREZOR using an OTG cable when asked. After unlocking the device with your PIN (and Passphrase), you will be prompted to select a TREZOR account. If you use more than one, you can choose which one to import. Repeat the import process to add more accounts.

Your labels will not be copied though. You will have to re-label the accounts on your phone.

That’s done! Now you have watch-only accounts on your phone, without the necessity to carry your TREZOR with you. Select your TREZOR account, open the ‘Balance’ tab, and use the QR code/addresses to receive bitcoins directly into your TREZOR.

Spending from a watch-only account

Since your TREZOR account can be imported into Mycelium as a watch-only account, it would be also convenient if there was a way to spend from it, right? It is actually very straightforward. All you need to do is to plug your TREZOR into your phone for the device to sign your transactions.

In Mycelium, select the TREZOR account you wish to spend from (marked by the TREZOR icon), scan a QR code, or enter the Bitcoin address you want to send your coins to, and select the appropriate fee. When prompted, plug in your TREZOR using an OTG cable. Enter PIN and then, after verifying the transaction, confirm it on your TREZOR. Done!

Spending without import

Spending from TREZOR through Mycelium is also possible without previously importing your XPUB. This may be preferable if you do not want to have your transaction history on your phone.

From the drop-down menu in Mycelium, choose “Cold Storage” whenever you want to spend your coins. Select TREZOR, and plug it in, when prompted. Don’t forget to verify your transaction!