Heat detection is an important aspect of fertility management. In the past, it primarily involved visual observations, whether or not supported by tail chalking. In recent decades, more and more smart technology has developed. A sampling of well-known developers: Afikim, Dairymaster, Nedap, SCR and Agis. Their technology is also used by a number of dairy equipment companies. Interesting is the development that some AIs offer heat detection systems to customers to support fertility results.