RPM for milk frothing?
The Ozeri Deluxe milk frother  claims an rpm of 15000 rpm

http://www.amazon.com/gp/product/B00BISKPMG/ref=as_li_ss_tl?ie=UTF8&amp;camp=1789&amp;creative=390957&amp;creativeASIN=B00BISKPMG&amp;linkCode=as2&amp;tag=nmjv-20 

However I have seen in ikea (and pound / dollar stores) a much cheaper option that to me seems much the same 

http://www.ikea.com/gb/en/catalog/products/30100041/

Hope this helps