Hide a keys that look convincingly like the object they are mimicking are probably significantly safer than those that are dead giveaways, which is why making your own can be useful. But keeping keys outside your home is always going to pose more of a risk to your security than not having keys outside your home. If using hide a key objects, incorporate other security measures to reduce the risks. For example, free apps like AlfredCamera could help put your old phones to use and act as an outdoor security cameras which will alert you when they detect unusual movements.