RSK is the first open-source smart contract platform for Bitcoin.
The goal of RSK is to give added value and functionality to Bitcoin's ecosystem by enabling smart contracts, instant payments and more system scalability.
RSK network can withstand 400 tx/sec (simple payment transactions). However, RSK goal is to reach 2K transactions per second using its Lumino technology. It will be possible to make Instant Payments, Payments in Stores and Shops and payments for Online Gaming.
According to the information from their site, RSK Platform will use Bitcoin as its original currency and have already released their network test phase while working on the final product.
Take a look at what RSK is all about on their site
https://www.rsk.co/What do you think about RSK and smart contracts for Bitcoin?