After joining me as moral support on a keto diet and losing quite a bit of weight as a result DH has started going to the gym which I'm really chuffed about as he had some weight around his stomach and quite a sedentary lifestyle, which isn't good now that he is over 50. He also has had depression in the past and has always been recommended to do exercise but just never got around to it. His aim is to get healthy. Though if he gets buff neither of us will be complaining. 
I'd really like to get him some sort of device that helps him measure his fitness etc (he loves tech) but I'm a bit bamboozled by the choice. He has a Samsung phone. I don't want to go bananas but want him to be able to track his exercise, sleep, stress etc if possible. As it's Black Friday I've been reading around but I'm just not sure what to get. Does anyone have any suggestions please?