The ARVI is a very powerful debugging tool if you want to do some software development on a C-64.

With the built in machine code monitor, you can stop code execution at any point and look into memory, start tracing your code, set break points for when something happens and of course modify your code on the fly.

Most "professional" AR users didn't really use the poke finders and spritekillers the cartridge provides, but mostly the BASIC extensions it provides and the aforementioned Monitor tool.

Nowadays there is a new version of the AR (based on the AR VI) called the Retro Replay.

That cartridge has an user upgradeable flash rom, more memory than the original AR and it also sports an Amiga 1200 clockport connector that can accomodate an rs-232 adapter (Silver Surfer) or an ethernet adapter.

Yes, you can connect your C-64 to the Internet using a Retro Replay, Silver Surfer and the Contiki OS!