I am considering a big brake kit and have been researching the many different kits. I too would prefer to have functional pad wear sensors.
Dinan claims that their BBKs retain the oem wear sensors. There appears to be a small pocket in the pad to accept the sensor. Because the Dinan kit is merely a re-labeled Brembo kit, it can be assumed that the Brembo kits will also retain the sensor. Stoptech kits use a different but possibly compatible sensor. See their website for more details. I don't know about the use of sensors with other BBKs.
Unfortunately the Dinan and Brembo kits are very expensive and the Stoptech kits are only slightly less expensive.