I do use a Basal body thermometer that I bought at Target like 3 or so years ago. I started to take the temp orally and found that to be to much of a swing in temp from day to day.
I have now started taking the temp rectally and that proved to be much more even. The trick with temping is that you would need to take it at the same time everyday even weekends (I have not been so good at the exact time). The temperature alone mostly shows you when you ovulated and not before. So doing a temperature and OPKs combo may work for you. For me I just check the CM and position of cervix etc for this. I recently started using
Ovulation Calendar and Ovulation Chart - Fertility Charting and that helps me chart all details that I need not just temp for the day.
I hope this helps.