I already have a (crappy old non-android) cell phone, it supports connecting a bluetooth headset to it to talk/answer/etc calls with, so you never have to take the phone out of your pocket. I'm wondering if there is an android app/hack/anything that lets your android device function as a bluetooth headset, in this regard. The crappy cell phone still is technically the one answering/making all the calls, but it would stay in your pocket the entire time. Since it'd be connected via Bluetooth as a headset, the Android device would be the thing that rings, the thing you talk on, the thing you hang up on, etc. Is there any such a way to do this? I tried searching Google, but 80% of the threads were unrelated entirely, and of the 20% that are about this, most of them said to use Google Voice (which is completely irrelevant). The other ones never found a answer. EDIT: I just found out that my crappy cell phone has Bluetooth sim-card access. If it's not possible to use an android as a headset, can I somehowly use my android to connect via bluetooth, and use my other phone's sim card?