I have. I bought a 3 point splitter from Tractor Supply. It's pretty slow due to the hydraulic flow available via the BX25, but I bought a nice new valve (1 SPOOL PRINCE AUTO CYCLE LOG SPLITTER VALVE W/PB). Kind of pricey, but it doesn't require me to hold the lever down which means I can be getting the next log ready while it works on the current one (it does auto-retract at the end of the stroke). Now if you're splitting smaller logs, this is great. For the bigger ones that have to be run through the splitter multiple times, you're left standing there for a bit while you wait for the slow hydraulics. I'm fine with it, maybe I'll upgrade to a pull behind splitter someday for more speed, but I'll make do for now since the total cost was probably about $1100 which isn't bad compared to some of the nicer standalone units.
I bought a 3 pt splitter at Harbor Freight a few years ago for my bx24. It's not fast but neither am I anymore. I usually mount it on the 3 pt hitch but I got hoses long enough that I can use it in a stationary spot without having to remove the backhoe. I've put about 50 face cords through it with no problems.