The iiBackpack is an ii / i2c bus expander for the Monome Teletype designed by Brian at Monome. It provides the ability to reliably connect 4+ ii devices to your Teletype.
The iiBackpack affixes to the back of your Teletype, connecting to both the Europower and i2c headers. It strengthens your II bus by supplying additional pull-up voltage to the lines. We've successfully connected 16 devices to our Teletype using this beast. It was awesome.
Build an iiBackpack yourself by printing your own PCBs from the Shared Project at OSH Park.