proximity sensor useful?

I was told that proximity sensors are really only useful for convertibles only?

Those of you who has it on a regular car, does it work outside the car? 

These things used to be pretty expensive.  now they seem really cheap

https://www.asianwolf.com/item.jhtml?UCIDs=1068694|1069136&PRID=1057682

The other thing I'm worried about is that the extra battery draw to power the sensor.  Can I wire a switch to only arm the proximity sensor when I want to.   I would think for short trips it's fine, if you want to park for a week, you might want to turn it off? 

Pooreclipse wrote:

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I was told that proximity sensors are really only useful for convertibles only?
true, you can use it on a hardtop as well.

Those of you who has it on a regular car, does it work outside the car? 
yes, I have a DEI 508D, I set the sensitivity so if you were to peek inside-it'll
set off the warn away. 

These things used to be pretty expensive.  now they seem really cheap
It depends on what you get.  remember-you get what you pay for.

https://www.asianwolf.com/item.jhtml?UCIDs=1068694|1069136&PRID=1057682

The other thing I'm worried about is that the extra battery draw to power the sensor.  Can I wire a switch to only arm the proximity sensor when I want to.   I would think for short trips it's fine, if you want to park for a week, you might want to turn it off? 
It does draw extra power.  I think it is draining my battery.  That's a good idea, I should try intergrating a switch to turn it off at times.

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Unfortunately, I DO have a convertible with the proximity sensor.  The thing about them is that they do not go through metal, so in a hard top they might not catch as much as it would in a convertible.  What I have done is added two additional prox. sensors under the trim below the side rear windows (the original was installed under center console)  This way I have a better field of protection, without having to have the gains/sensitvity way up.  Now I find the system is not as sensitive to false alarms... but it is much more accurate than the single one was!..  As for the power draw, I have never had a problem even leaving the car up to two weeks between starts.  My installer even added a mini piezo siren for just the warn away.. and with three prox sensors I still have never had a problem.  Oh, and my installer told me he could install a relay up to one of the additional chanels to by-pass the prox. by remote if I wanted to... just a thought.