I just learned about Kovri and it seems to be a new trend for coins to hide the senders IP. What other similar implementations are there for other coins?
The network layer is different from the blockchain layer. This feature is provided by the wallet, not consensus.
The Bitcoin Core wallet includes a mechanism to connect through Tor. Several other forks of Bitcoin offer this feature.
I2P is less-frequently used, since it requires more network participants to use the service. This was first used by Anoncoin.