Of course "the easiest way" is to make an online wallet (i.e. own a server). This way allows to validate hypotheses that this kind of service has some additional value to users.

But I like the way of how Jan explains his view on features a wallet have to have (https://bitcointalk.org/index.php?topic=37709.0). I mean that there should be several type of wallets, with small sums for easy use and less secure, medium and passphrase and/or 2FA, rest with the most secure way of storage.

So messenger version is for "small" one. But I also digging/thinking to implement features like word seed, passphrase, 2FA. For instance how this is done in Elecrtum or other wallets. Seems like it is possible.

I'm making wallet as a service in messengers. First prototype I'm going to make for Telegram.

What do you think about following issues:

1. possible security holes/issues/problems
2. potential use cases. Here most valuable information will be
  a) how many transaction do you usually make
    - one in a month or less
    - several in a month
    - several in a day
  b) how do you send tokens
    - through exchange
    - peer 2 peer
    - from my wallet
      - offline wallet
      - online wallet
  c) have you buy something for coins? What was that?
3. what problems do you have (if any) using current methods of sending coins/tokens.
4. Anything else what bothers you?

Thanks to view this post.