I put together a programmer for ATTiny 25,45,85 based on a ESP8266.
This uses the 12V high voltage method to allow it to edit fuse settings, and read and write flash and EEPROM data.
It uses a browser interface to control it and can store and read memory data using hex files. This makes it easy to back up, restore and program new data. This includes installing or re-installing the micronucleus bootloader programs.
Details are at https://www.instructables.com/id/ATTiny-HV-Programmer/
This has construction details and links to the software used.