For me smartphone as arrival sensor never worked very well. Very unreliable.
I have been using Samsung’s arrival sensors for about a year and just wanted to share some experience and tricks that I have learned. Since my sensors disarm the alarm, I’d rather not have it on a keychain.
Operation.
I have sensors in the car. Car is parked in the attached garage. There is a fairly good zigbee coverage. Sensors disarm the house alarm. From time to time (not often) sensor does not report arrival in time before I open the entrance door. To get around this issue I put 2 sensors in the car. It is an added expense, but likelihood that one of the two sensors will report presence in time is very high for me. I don’t remember triggering the alarm after adding the second sensor. If for someone that still doesn’t work reliably or don’t want to spend extra money, the trick is to simply add a bit of delay before alarm sounds, so you can disarm the system at the keypad in a rare case when alarm is not disabled by the sensor. You can also simply check for the sensor presence in 15 seconds after opening garage entrance door, before activating alarm. I think it is not too difficult to go around the sensor delay in presence detection.
Battery.
Like everyone else I have noticed right away the poor battery life. I must say that after 3rd pill battery installed, I have noticed that battery life was a bit improved. It got to 15% very fast, but then stayed at 15% for a long time. Not wanting to deal with battery/reliability issues, I hacked it. I see that similar hack was already suggested, but here is mine simple solution:
This holder has 2 AA batteries supplying total of 3V needed for the power. Just connect (I soldered) two wires to the contacts, attach sensor case to the battery case (I glued mine together) and you’re done. Very fast, cheap and simple fix to the issue.
I can’t believe that Samsung or one of the Chinese manufacturers didn’t come with a car arrival sensor yet in a bigger case, with much bigger battery and faster polling (if protocol allows).
Meanwhile I think somebody with more time of their hands can actually make some money building these from available parts, so people without experience don’t have to mess with it.
Arrival sensors can be had for $15 on sale (currently about $20 I think).
Battery holder is about $2-3.
One can easily put together at least 20 of these in one hour and sell for $35/ea with $10/ea in profit after parts and shipping.
Just an idea…
Meanwhile since I see that there is no product/improvement in this field after more than a year, I guess I will just have to get the same sensors again for another car/member and fit it if with the battery.