Note: for best results, use with the app developer's proprietary line of Bluetooth headsets.
I've searched all over the Android app market, and found several neat apps (2 specific examples are "Locale" and "Setting Profiles") that allow you to activate various phone settings when triggered by a variety of conditions. For instance, you can set it to activate your WiFi at a certain time every day, or activate your Bluetooth when your GPS chip detects that you're within a certain distance of a specified location, or without (?) a certain distance.
The Setting Profiles app allows you to activate Bluetooth as soon as you receive a call. This is a neat idea, in theory, except that activating the Bluetooth in many devices does NOT automatically put them into connection mode. One must still navigate to the phone's settings menu to tell the phone to connect to the paired device.
My idea is twofold, and designed to prolong the battery life of both the phone and the headset.
First, is a simple modification of the existing app technology. Activate the Bluetooth, and connect to the headset that you've previously paired with it. I timed my Motorola Cliq XT on its connection time. From the second I clicked the button to activate the Bluetooth and connect to my Motorola headset, it took 19 second. Standard maximum ring time (the length your phone will ring before going to voicemail) on a GSM network is 30 seconds. This means that I could answer an incoming call with 11 seconds to spare.
The advantage of using such an app, of course, is to prolong your phone's battery life by keeping the Bluetooth radio off when not actively in use.
The second part of the idea is a Bluetooth headset designed to take advantage of this app to prolong its own battery life as well as the phone's.
It has a passive audio pickup that is on during standby mode. I'm confident that this will result in slower battery drain than having the Bluetooth radio running in standby mode.
When the phone app detects an incoming call, it emits a high- frequency beep which is detected by the passive audio receiver on the headset. This activates the Bluetooth radio on the headset and puts it in pairing mode. Simultaneously while activating the Bluetooth radio on the headset, it activates the Bluetooth radio on the phone. Headsets usually activate faster than phones, so by the time the phone's Bluetooth is activated, it's immediately ready to connect to the headset, which the app handles seamlessly.
After the call ends, both devices go back to passive standby mode. The importance of activating both Bluetooth radios as near-simultaneously as possible is that headsets only stay in pairing mode for about a minute after powering on. What this means is that even with the app functioning perfectly, it won't work unless the headset is actually in pairing mode, requiring both good reflexes and timing on your part to activate it as soon as you get a call.
This is why I suggest using the proprietary headset, which handles this for you.-- 21 Quest, Mar 11 2011 There are a good many features in the Android market I'd like to see. For instance, why does HTC feel that displaying the little green man is more important during a call than having numbers? And why can't I refuse a call simply by hitting a side-key instead of digging the silly thing out of my pocket?-- RayfordSteele, Mar 11 2011 I think there's an app that allows you to change the action of the volume keys... not sure if you can reject calls. I'll test it and get back to ya.-- 21 Quest, Mar 11 2011 @ Ray, check out an app called "button remapper". Requires root access, and the only 2 comments on it both claim it permanently broke their home key after remapping them, but it might be what you're looking for. My MyTouch and G1 (both HTCs) both have dedicated send and end keys, so they're easy to dismiss a call with. Haven't tried side keys on my Cliq XT.-- 21 Quest, Mar 12 2011 random, halfbakery