PayPal Mobile SDKs are Deprecated. The APIs powering them will remain operational long enough for merchants to migrate, but the SDKs themselves will no longer be updated. Please use Braintree Direct. Paypal's iOS SDK allows developers to add a PayPal payment option to their mobile apps. The SDK currently supports single and future payments as well as profile sharing.
Bitpay's API allows for businesses and employees to accept BitCoin for their services and goods. Now with the addition of Newegg to it's repertoire of business affiliates, BitPay is receiving more credence as a leader in the march toward the legitimization of BitCoin as a secure digital payment system.
Venmo transactions are still easily obtained by the public according to computer science student Dan Salmon, who says that he accessed millions of transactions over a six-month period in an effort to raise awareness about privacy on the popular PayPal-owned peer-to-peer payments service.