Well .. the big one of these is GPUs, which started as fixed-function pipelines and turned into massively parallel execution systems repurposed to cyrptocurrency.
Various people have tried to do niche things such as neural net coprocessors. General-purpose or GPU-like or DSP-like systems tend to win in the market ... because they're run on software, which is more flexible.
There's a reason ARM are now up to 180 billion cores shipped; the easiest way of making a custom IC is to wrap it around an ARM core with some firmware. The code is burned into ROM (which has security advantages and disadvantages!), but to me it still counts as "software".
At some point the iPhone will cross the triple digit of number of CPU cores onboard (counting across the whole board, not just the SOC and radio). It will be rather difficult for anyone other than apple to count when that is.