I am working on TIPI, with ElectricLab. It is an open sourced work in progress interface between a TI-99/4A and a Raspberry PI, so that we can provide a 'hosted' filesystem for the TI and leverage networking capabilities of the Raspberry Pi. The initial designs are prototypes. ElectricLab has a pair wire-wrapped logic boards using 7400 series logic to address memory mapped IO with the Raspberry PI. He has built some really cool software off of that to get two 4A's interacting.