The Milk & Tickles colour changing feeding bottle has a number of great features:

BPA Free, non toxic and reversible
Standard 250ml feeding bottle size that fits most standard sized teats
Heat sensitive - colour changes from blue to pink at 35C & back to blue when below 35C (So never feed your baby a bottle that is too hot again). Note: not designed to be a safety tool.
Body temperature changes the colour - make hand prints and designs - great fun for babies and toddlers