Nicole Kidman and Keith Urban are keeping their love alive by sending steamy text messages to each other! Now married for almost four years, they are often separated while she’s on movie sets or he’s touring with his band. “Nicole confided in her close friend Naomi Watts about how hard it was for her and Keith to spend time apart,” an insider tells In Touch. “Naomi said that when she and partner Liev Schreiber had to be in two different places, they hid little love notes all over the house and in each other’s suitcases to spice things up.” It sounds like Nicole took her pal’s advice: “Now, Nicole and Keith write sexy love notes to each other via text or e-mail,” says the insider. “It’s added some zip to the relationship.” Sunday’s parents “look forward to each other’s sexy notes,” says an insider.