And after the devices were released, severe vulnerabilities such as heartbleed were found.
https://nakedsecurity.sophos.com/2016/08/09/900-million-androids-vulnerable-to-quadrooter-bugs-what-you-need-to-know/
Also any other security bug found never gets fixed. This can compromise the device and eventually steal all funds on the phone.
Yes, true. I believe that there is no device that is ever totally safe as long as there is a connection to the internet. I feel somehow safe on IOS but under the line I'm paranoid when it's about security and usually I use an offline-Computer to generate keys for cold storage.
When it comes to Lykke: I'm not totally sure right now, but I believe at least it might already be possible to do the step with the 12-backup-words offline. But, more important: Of course it's work in progress and they really have a focus on security and also user friendliness and Lykke also won't be just about App's in the future.
Lykke is one of those projects that will grow in many ways/directions significantly and it's hard to know exactly how it will look in future. It's much more complex as it might seem now and also already bigger than many recognize. But I believe progress will happen pretty fast in comparison to others, because of the big team that is working on this.