Your smartphone can do many things, but because of legal restrictions, it can't easily be used to record a conversation. This Bluetooth handset happily will, though, documenting over 340 hours of calls, whether or not the other party knows it.
In most areas, the act of recording a phone conversation isn't necessarily illegal. It's when you do it without the other party's consent that problems can arise. So this handset, which connects to any Bluetooth equipped phone like a headset, can be set to automatically play a custom "this conversation is being recorded" message before every conversation. But only if you want it to.