TL;DR: What wallet apps are there for android (or sailfishOS) that has "true" support for multisig?
Thinking a bit, if I'm to possess serious amounts of bitcoins, I want a well-secured savings wallet - or, eventually just a well-secured savings address. After some thinking, the requirements seems to be:
1) it should not be easy to withdraw funds, withdrawing should either involve multiple people or the passing of a time window.
2) the bitcoins must be secured against my death
3) the bitcoins must be secured against loss/theft of a private key
One stupid-simple solution would be to generate a single private key, write parts of it down on 5 papers in such a manner that any three out of five papers needs to be recovered to learn the full private key, seal the papers in envelopes, and then distribute those envelopes to people/locations I trust, instructing them to keep them in a safe place and hand them over to my next in kin in case of my death. It actually seems like a decent way to solve this.
Anyway - why bother with such obscurity when bitcoin supports multi-sig transactions out of the box. Even for daily usage patterns multi-sig seems like a good idea. As for a savings wallet, I think that in the start it would suffice with 2-of-3 - me and my wife, plus a third arbitrator that can help us out in case of death or divorce. Armory seems to be the go-to-wallet for the Linux desktop - but I'd like access from mobile devices as well.
Apps tested so far
- copay - it could do the trick, but it seems to be a "lock-in platform" - all signing parties needs to have copay installed. That's not acceptable. For one thing, I want a platform neutral solution, like a savings wallet I'd mainly access from a "proper" laptop/desktop.
- "bitx smart wallet" - what kind of beast is this, requiring me to verify my email before use?
- greenbits/greenaddress - seems like their "multisig support" is very narrow; only 2-of-2, with their servers acting as one of the signing parties, and offering to sign against 2f-authentication. Totally not what I want.
- yet another android wallet that came up when searching for "multisig" - but it apparently had no support for multisig.