i love ergonomic keyboards and chairs. They're designed to minimize muscle strain, and i think that's an important issue today!
wow, tell me more 
Well for a good keyboard, I use one in the shape of a V so that both my hands can be at an angle, and it's more natural. No more muscle strain!
when did this trend start?
Well there was a contoured keyboard developed in 1977 that changed the arrangement of the keys to shoulder width!
Which company have the best of these ?
typical straight keyboard.
An "adjustable split keyboard" has the keyboard split into several independent pieces, so the angle between them can be easily changed.
Types Contoured keyboard.
A further development of the split concept are contoured keyboards like the 1977 Maltron or the newer Kinesis Advantage line, which place the keys into two depressions set approximately at shoulder width, with function keys set between the key groups for use with the thumbs. In this configuration, very little movement of arms and wrists is required.
Types Handheld keyboards
Ergonomic keyboard
An ergonomic keyboard is a computer keyboard designed with ergonomic considerations to minimize muscle strain and a host of related problems. Typically such keyboards for two-handed typists are constructed in a V shape, to allow right and left hands to type at a slight angle more natural to the human form.
Types.
Types Split keyboard.
A "fixed-split keyboard" is a single board, with the keys separated into two or three groups, allowing the user to type at a different angle than the