Not sure if you're looking for mobile or handheld.
Both the Kenwood TH-K20A and Kenwood TM-281A will listen for the NOAA tone while scanning. -However- the radio has to switch over to the WX alert frequency every 3 seconds to listen for the tone, which means that while you're listening to a frequency, every 3 seconds there's a "pause" in the audio as the radio switches over to the WX frequency. Also, it cannot listen for the WX alert when transmitting. It also does not do SAME local alerts.
Both work for WX alerts, but no where near as good as an actual WX Alert Radio.