I use the SM10 on my motorcycle and keep it plugged into external power at all times. I would like the ability to ignore the battery and just automatically turn on or off with external power, so it would come on when I turn the bike on and turn off when it's off. (External power is through a DC-DC converter running off the switched power of the bike.) Of course there should still be an on-off switch so the device can be permanently turned off regardless of external power.
This can either be a version of the SM10 that does not have a battery, or a switch added to the unit to enable or disable battery discharge. (Charge should always be enabled or the battery would drain away, of course.)
That would be ideal, but a simpler alternative is to just swap the pair button with the on-off button, because the former is so much easier to use than the latter, yet you only ever pair your device once, pretty much, yet it's turned on/off constantly.