Are you just looking to monitor temperature? I sadly do not have any sensors I could recommend based off of personal use. I have been intending to give one of the Qubino micro switches a try that offer support for a remote temperature probe that can measure between -50C and 125C. Take a look here: http://qubino.com/products/accessories/
EDIT: Please note that the Qubino products are also not certified to work with SmartThings. I believe there are users on the forum that are using these with success but I believe they will require a custom DTH. See [RELEASE] Qubino Flush 1D Relay, Flush 2 Relays, Flush 1 Relay, & Flush Dimmer
EDIT2: Note that these are Z-Wave senors and they make versions for every region of the world and a sensor made for one region will not work in another (Z-Wave frequency is region dependent) so make sure the region of sensor matches the region of hub (Most likely US). I may have made this mistake when trying to order one of these in the past… 