For a while I have been thinking it would be interesting to write the uC code for a Dallas 1 Wire slave.
Either it is an unpopular idea, or it has been discouraged by the Maxim Dallas people. About 2 weeks ago I found a vendor document stating that they have not allocated any device addresses/types for 3rd party use. About the same time I saw what was untested BASIC code.
I admit I've never thought of using the Maxim/Dallas 1-wire protocol.
I have however implemented a much higher speed Icom 1-wire (open-drain) CI-V protocol on a 12F683 based Ham radio accessory. The CI-V protocol uses standard serial data (8/1/N) at 5 volt TTL levels which necessarily limits the 1-wire bus length to relatively short distances. The packet protocol includes two header bytes ($FE, $FE), "To" and "From" address bytes, variable number of data bytes, and an $FD end-of-record byte.
I have been using 1 wire sensing (mostly temperature) for over two years and find them to be very durable. I have them outside, in the greenhouse and garage, and koi ponds.
In time I would like to create a monitoring, control, and security network. Speed is not important but not having to make repairs is.
There are some functions that the available 1 wire products do not address. A DIY slave based on a uC would fill the void.
I have thought of doing this a few times. You could just make your slave look like a DS18x20 but return an invalid temperature (+127) when queried so you know it is your slave and you can then send it any custom commands you like. I thought of programming a 509 to act as a slave so I²C/SPI devices could be added to a OW bus. An obvious omission in OW devices is a humidity sensor.
<edit>Implementing the searchrom algorithm would be fun. I have managed to implement the searchrom and send RS232 on a 10f200! Fitting that into 256 words was a challenge.</edit>
They have discontinued the DS2423 counter which was popular for building tip bucket type rain gauges.
I doubt one could put together a setup using parasite power but it is worth looking at. If not you will need a 3rd conductor or provide local power for the custom devices, maybe solar. Would be interesting.