Basal thermometer - which one to buy?

[Gillian1980]

As it says in the title really!

I'm thinking of monitoring my temp and was after some recommendations of which one to buy. I've seen lots if cheap ones in eBay but if they're useless then I'd happily spend more for a good one.

Thanks :)

I have this one.

I've had it for 4 years now and although I didn't use it for 2.5 of those it's still working.

Thanks Terry's :)