I had my phone and FOB together in one pocket and still everything worked fine but there is possibility of interference by doing so, also battery may drain faster due to constant interrogation of the signals emitted by both devices close to each other. Keeping one device in pants pocket and another in shirt, or something similar should avoid any problems, but honestly, in real life shouldn't be big deal. I keep both devices in separate pockets for totally different reasons: I want to have easy access to my phone in case of phone call, I want to keep my FOB in most secure pocket so I won't loose it: so keeping FOB in shirt pocket is out of the questions, too easy to fall out when running or bending down, for similar reason keeping phone in pants pocket is almost impossible to take out quickly when sitting. Even woman's handbag should have separate compartments and few inches distance should be good enough to avoid any issues.