The way the Bitwala Bitcoin wallet is designed is actually pretty safe. When creating a wallet, you get an encrypted backup of your private keys which can be used to restore your wallet independently of Bitwala. We never store your password or your keys (and can't help you restore them, so make sure to keep your backup sheet safe!). That being said, please also use hardware wallets! We do support and encourage the use of Trezor on our site.
RE: Bitwala launches the Bitwala Bitcoin wallet