I have a handful of the Iris contact sensors. They work great but are big and bulky.
What are some of you using that are almost invisible for windows and maybe doors?
Are the Sensative Strips the only option? (they is a pricey).
This would be for existing construction.
I may be happen with something between iris and the strips ...
I have a few of these and they are working well so far.
I like the monoprice zwave plus sensors. Both the external and recessed types. Can't beat the price either.
I would avoid the monoprice recessed devices. They don’t work well with exterior doors or patio doors. I have them on all my exterior entry points and have a 5% failure rate of accuracy of open/close due to radio interference with metal doors. This causes automation failures all the time. 
Got my hopes up ... thank you for the advice.
The Aeon Recessed Door Sensor and the Monoprice Recessed seem similar, but close study shows the Aeon to be better. The internal PCBs are different and the magnets are different too. I've relegated the Monoprice device to be a Lab device only. All the doors I put it in would be just a bit flakey.
Another poster had nothing but complaints about the recessed door sensor, but the bulk of the complaint seems to be related to how "well stuck" the outer plastic case is to the door frame. The wood swells and he said it warped the case. I have never had that particular problem, but I blamed that on my wobble drill skills. I'm perpendicular challenged I suspect. By the time I get it to fit flat, it's never "too tight."
Is this the one you're talking about?
https://www.amazon.com/Aeotec-Recessed-Invisible-security-Battery/dp/B0151Z49BO
@ $36 I may just bump up to the sensative strips or wait for the zigbee ones if they ever show up.
The Sensitive Strips have embedded batteries. I've had a couple weeks last year when I was experimenting and ended up hitting the battery devices so often a new set of batteries would last 2 days only... they are supposed to last a year.
Don't let that happen with the Sensitive Strips, OK ? 
Replacement CR123a = $ {way less than a new Sensitive Strip}
Valid point - very valid.
I like these as well--they're pretty small, have a very low profile, and the price is pretty tough to beat. Specs list dims as: 66 x 25 x 10mm (approx. 2 5/8" X 1" X 3/8").
Ditto on the 340e's. Cheap and work. I use these in cabinets inside the house as they are easy to fit in smaller spaces and not get in the way. I've used the Aeon and Monoproce internal door sensors and I've had really good luck with them also.
Hmm. I have several Iris contacts and don't find them that bulky, but they do stick out about as much (plus a bit more for the case) as the CR2 battery they hold. I always thought the Visonic looked bigger, but I guess it's just flatter and sticks out less at the slight expense of other dimensions. I don't doubt they'd look better in many places.
Xiaomi sensors are quite small and I think the Aqara ones look quite nice, but they are non-standard ZigBee devices. Many people get them to work well, but it is a slight risk and does require some extra effort to pair (and stay paired).
I have a few of the Monoprice (non-recessed, PID 24259) and HomeSeer contact sensors, and they are bit large, but perhaps less deep, which may be the concern here. They look identical and are likely the same hardware. These devices also have a "tamper sensor" (small button on the back that is normally pressed in when it's mounted to a solid surface and sends a message to the hub when it gets un-pressed, indiciating the device was probably removed from the door/window/etc.) if that's of any interest.
The ST Multisensor, including the new/2018 version, also is less deep than the Iris, but it's probably taller than most/all of the others (but not as wide as the Monoprice/HomeSeer). It's also a lot cheaper, $20, than it used to be. I found the old generations to work well too, and they're a similar size (but the last gen--was it v4?--was probably a tad smaller than this one), with the exception of the large first-generation/KickStarter-era sensor. ST users have given the last and possibly current gen some bad reviews, but they've been working well for me.
So I may not be absolutely correct with my statement. I just discovered that my recessed monoprice contact sensors were connecting to HE via secure zwave. HE support explains that the calls to/from a secure device is triple the burden to both the sensor and HE. After I unpaired and repaired without secure zwave I haven’t had ANY issues since doing this. So my review was skewed and I apologize.
I suggest Xiaomi door and window sensor or Aqara door and window sensor. The both are quite small with good quality at low price.
Definitely good prices, quality and performance if you have them close to the hub or have an XBee, Sylvania Smart+ (non-version A) outlet. Purportedly IKEA Trådfri bulbs. and Initial tests here seem to suggest that also the new IKEA Trådfri Outlet may be compatible repeaters, but statistics have not been obtained for those last two. Hang loose, we'll know very soon.
[Edit] IKEA Trådfri Outlets and Trådfri Repeaters are the best choice for low cost repeaters for Xiaomi
I have three Monoprice recessed door sensors and they work flawlessly in my three exterior doors. The battery lasts forever and notification was instantaneous even on ST.
Is there a US seller? Seems like all of them are "ship from China." I don't mind waiting the 2 weeks, but I admit to really really wanting to play with these now.
AliExpress is certainly a legit retailer, but slow as hell to get to the US. Even the sellers on NewEgg say shipping from China.
Aqara Official will launch products on Amazon soon (The news from their official website). But I think the price is higher than those on NewEgg or Aliexpress.
I'd gladly pay a few bucks more to have it shipped from the US.
Just a guess, but the newer version products they plan to sell in the US may be more than just a few bucks more expensive. I believe the reason the previous generation devices were so inexpensive is that they were never really intended to be sold to US consumers.
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