The Requital, a thriller by Bruce Allsman

Dr. Avinash Gupta is a billionaire, a domotics pioneer and inventor of ISHANA, Integrated Smart Home and Networked Appliances, a state-of-the-art home automation system. Avinash and his wife, Shayla, live in their new home that is equipped with ISHANA. When unusual things begin to happen, he investigates and discovers that a malicious hacker, Peter Newman, a former employee with an axe to grind, is gradually taking control of ISHANA, in turn the home's hermetic environment thereby trapping him and his wife. Peter demands a huge ransom, an immediate payment by wire transfer, or he would use ISHAHA to kill them.