Bracelet for temping? Getting frustrated!

Does anyone know of an accurate yet wearable body temperature sensor? I was thinking about a fitness bracelet that also monitors body temp, but it appears this function isn't common in fitness bracelets. I've seen wearable sensors for children, but these aren't meant for everyday use. I can't temp in the mornings because my waking time varies considerably. My work schedule changes every 4 weeks...I also work every other weekend on top if that. Some nights I get very little sleep working on projects (and I need to catch up on sleep on my weekends off). TTC #1 x 4 months. Long cycles (>45 days). Age <30.