Some background: It's an Android wallet, where you maintain a euro balance (held by Bridgewalker for you). Using those funds, bitcoins will be bought at current market price whenever you want to send any. This allows you to use Bitcoin only as a payment mechanism, without being affected by the exchange rate volatility. You fund your account via Bitcoin as well, which will be exchanged for euros at current market price and credited to your account.

So: Bitcoin as transaction mechanism, Euro as store of value.