A few days ago when I searching the App Store for a bitcoin wallet, I found Bither. It's just like the kind of wallet I've been waiting for. So I became excited, installed and tried it.
Bither has two modes, "hot wallet" and "cold wallet". You need to install Bither on two devices and both Android and iOS versions are available. The cold mode can't not run when the device is connected to the internet. Typically, you keep the hot wallet on your daily phone and the cold wallet on a backup device. I tried the cold wallet on my 3 years old Android phone, and the hot wallet on my iPhone 5s.
Hot wallet can monitor addresses generated on the cold wallet. You can spend your bitcoin from monitored addresses with the hot wallet. The hot wallet makes an unsigned transaction QR code which you can scan with your cold wallet. Then you sign it on your cold wallet which in turn makes a signed transaction QR code. After you scan it with your hot wallet, the transaction is sent to the network.
Even though the concept is a little complicated, it works well. And it seems really safe. I think Bither has found the balance between safety and convenience in keeping bitcoin. I can't see any easier solution as safe as this so far.
As I said, I'm excited about it.
And I found a demo video about it.
https://www.youtube.com/watch?v=Q1DSrc7qkrs
