I would steer clear of a house warming gift geared towards just one person in the family. Tools are a great idea but your friends wife may not appreciate them as much as him.
I just went to a family celebration for the kid of a niece whose marriage I attended 20 years ago. I'd emailed them recently congratulating them on the anniversary. My wedding present had been a cordless drill, which obviously had the husband in mind, he's a handy guy and all and works for the Navy, managing construction projects. So, over this last weekend I brought with me a couple of professional KitchenMaid silicone spatulas, like the ones that get daily use in my kitchen. I included a handy brush to clean them. I also included a couple pairs of gloves for the fella. When I gave him this stuff he said that he's the one who would be using the spatulas, i.e. he does a LOT of the cooking!
I don't know if these folks who just bought a house are into cooking, but figure most people are to some degree. I think a kitchen scale well chosen stands a good chance of being appreciated. Mine gets used constantly.