Looks useful, but pricey... the DIP version is $9. But from reading the datasheets - is it just a specially programmed PIC?
Well maybe - but if you want to debug an I2C or SPI slave device then its good to use something thats proven. Sure - we can all write it ourselves - but only AFTER we know what we are doing!! Its really hard to write this stuff if you don't have an I2C, or SPI, compliant device to test against.
Not sure if you are talking about the more flexible IO expander or not - when you mention $9. But that is a very flexible device and one you would breadboard for debugging usage and use another hardware implementation on your own board once debugged.
I see it as:- buy, breadboard, debug, learn and then build something more dedicated. So I would use it as a development/debug helper.
But hey - this was just an 'advertisement' - I have no knowledge and no experience of it for now.
If anyone gives it a go then let us know.