Yes, macegr, luksedj, thats exactly the stuff I was thinkin of when I added the mode
Single channel "battery saver" sensor :
In this mode the user can cut a trace and add a jumper to disable Oscillator A, so the TX alternates between Osc B and radio silence. The 555 is setup per all the data sheets and tutorials, using a good sized C2 to increase the time as wanted. Use a large R4 and a small R5 to make the duty cycle as low as desired, even a few milliseconds every few hours if you really wanna get carried away with battery savings. The normal 555 timer circuit duty cycle is 51% to 99.999999% so Osc B is the one we want to use for battery saving, as U1C inverts this into 49% to 0.000001%.
I think the limit on duty cycle is how vigilant your Arduino sketch can be and how quickly it can aqcuire the pulse rate to your desired accuracy before the burst is done. This hardware can probably exceed what the sketch can do, so dont make R5 too small !
Of course this little hack cant do everything, but IMHO its quite a versatile circuit for dirt cheeep simplicity, which is what I was striving for.
The holidaze are over, hit it hard in lab all day, no proper lunch, and am just now home. If enough folks are interested in things this can do it would be nice to get together some prototypes to play with. But, alas, the holidaze are over...