Are there any Bitcoin wallets with native I2P integration?
C++ may be viewed by some as more suitable for Bitcoin use than Java which I2P currently heavily relies upon

https://github.com/monero-project/kovri

Kovri:


To cover, veil, wrap (Esperanto). 
A secure, private, untraceable C++ implementation of the I2P anonymous network.


Once complete this project should ease of integrating Bitcoin in both a private and secure manner.