In short, what I need are service recommendations that have the following characteristics.
. Multiple currency options (the more the better), mainly: BTC, ETH, LTC, DOGE, TRX
. API for generating payment addresses and sending payments
. IPN for notifications of payments received
. Custody of balances, because the balance needs to stay in the account until I decide to withdraw it or make payments when necessary
The first and last point are really not compatible with each other. If you are sending an API request to a 3rd party service, you are trusting the service to give you an accurate response, even if you have the private keys associated with the address they are supposed to be giving you. If they return an address that you have the private keys to, you will remain in custody of the bitcoin, however if you are given an address that you don’t have the private keys to, you will not have control of the bitcoin.