Kovri is an open-source side project that attempts to bring more network security and privacy to cryptocurrencies. Though it is being built for Monero, it will feature a common API that can be used by any cryptocurrency or project.
Kovri is an anonymizing router that protects network participants from leaking unwanted information. With Monero, it will mostly be used to break the possible association between transactions and the IP addresses that send them. However, it could be used in extreme cases to hide all Monero traffic, allowing people to run nodes privately.
Beyond privacy, Kovri provides additional network resiliency. It prevents attackers from blocking certain transactions from a controversial person, internet service providers from slowing Monero-related traffic, and more.