well, I never hatched chickens but I 'accidentally' hatched some tiny Komoris Day Geckos....no breeding set up, did not know they were already mature enough to mate and never expected any of the eggs to hatch as they are difficult to breed and I never had geckos before.... I have several geckos but only had one unsexed pair that I raised in one tank and then housed in their individual tanks - waited too long, they mated successfully
I house each gecko in a rainforest style terrarium and have hygrometer/thermometer from reptile supply place in each. I somehow managed to maintain temp and humidity at appropriate levels and successfully hatched a total of 5 (the eggs were laid in pairs, so three times success (one with only one hatchling), one failed hatch). I don't know if anyone has tried them or has experience with them but they were not too expensive as I recall and seemed accurate enough....