What multi-sig wallets are there for Android/Jolla?

Question

TL;DR: What wallet apps are there for android (or sailfishOS) that has "true" support for multisig?

Requirements/rationale

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

Solution: multisig

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.

Answer 1

If I go slightly of topic I will recomend you to incorporate a solution using a law of trusts if your law system has it incorporated.

I am still about to recommend you Copay wallet as it is open-source. You can even rebrand it to your own company.

You have to remember that you can use HD wallet with Copay. You can use Bitcoin Trezor with copay so you have strong security. And all of this could be saved to a secure place.

Answer 2

Use coinb.in It allows you to make multisig addresses from public keys, create transactions to spend from multisig addresses, sign transactions, verify transactions and broadcast transactions. You can run the website offline with full functionality (except broadcast of course).