Most Best Buy seem to have the peq sensors on sale in store right now, but they are not on sale online. Lots of community members have them. They are not officially supported, but most of the sensors work as generic devices. No custom code required. I have two of the contact sensors and one of the motion sensors. Note that other devices like the cameras, thermostat, etc. will not necessarily work with smartthings. But most of the sensors are rebrands of a different brand which does work with SmartThings.
Much discussion in the topic @greg linked to: