Additional questions as current post maybe too long to read for some users… 
Fraud protection
Could you go into more detail about this, as I think you don’t have a passcode on the app itself?
I appreciate others have explained why this should or shouldn’t be an issue. However I view it like a house, you have a good lock on the front doors/back door (access codes to the phone), but you might keep your valuables (monzo/pictures) in a safe (additional passcodes)?
There is a partial trade off usability vs security
Q: Should you use Monzo, if your security and privacy are more important to you than convenience?
A: Given that Monzo make it very difficult to revoke API access, don’t have pin protection for the app (on Android), show previous security questions and answers visible in the app (which is usually unprotected), and a number of other issues, it seems fair to conclude that Monzo generally prioritise usability and convenience over security and privacy. Thus, if you do not share this view you may consider alternative options instead.
If I was to invest in Monzo, how are you mitigating costs if fraud happens and people make off with mine or others money? I appreciate you have reserves as mentioned here
“…a very small proportion of your money (around 10% of total deposits) will be lent to Monzo customers in the form of unsecured personal overdrafts.
The rest sits in cash in our Reserves Account at the Bank of England or be used as collateral for payment schemes.”
Monzo Investment Ethics