BlueWallet is a free opensource Bitcoin wallet exclusively for iOS. It has a flexible fee system where the user can choose which amount to pay (starting from 1 Satoshi) and it will affect the transaction speed, the more the fee value, the fastest the transaction.
It's open and free and the security is a bad side of, I wouldn't risk to deposit a big amount.
I know the rule not your keys not your money. Bluewallet is fine for a small amount
The flexible fee seems high. It could be much more less.
The review said that the fee is flexible. Well, I think it could be more flexible. It's still high.
The transactions go through fast. Stable platform.