I have a working version of optiboot as well for both tiny85's and tiny84's. As you say it does require the oscillator to be tuned, so I am currently working on including tinyTuner in the bootloader when you first burn it which will then callibrate the oscillator and store the calibrated value in program memory and apply it each time it loads.
My version of optiboot for the tiny's is 576 bytes, which is a bit smaller than the stock version as I made several other enhancements to make optiboot smaller - using unions in some places for example.
Once I have got the TinyTuner code added (it wont increase the size of the bootloader as it will be overwritten when you download the first sketch) I will release my bootloader, along with a partly rewritten Tiny core I am working on.