Compatibility of bar end shifters and 10 spd Tiagra I want to try an aero bar type set up, with bar end shifters on my 10 speed Tiagra road bike, do I need a particular bar end shifter to do this?
With Tiagra in particular this answer is different from if your bike had any other 10-speed group.

Presently there are two different 10-speed Tiagra generations, 4600 and 4700. (So the STI from one is ST-4600 and the other is ST-4700, etc). 4600 uses the same classic actuation ratio that all pre-11-speed Shimano road groups used other than first generation Dura-Ace. 4700, however, is an oddball group. It's 10-speed but uses the new 11-speed actuation ratio, resulting in a situation where ST-4700 is currently unique in Shimano's history in terms of number of clicks (10) and amount of cable pulled per click. No other shifters interchange with ST-4700, including any of the bar-end models. So if you have 4700-level Tiagra the answer is no, there's no way of doing this. You would have to also get a new rear derailleur from any other 10-speed road group, like for example RD-5600, RD-5700, RD-6600, RD-6700, RD-7800, or RD-7900. Then it will work. (The front derailer will be friction so no issues there - otherwise it would also have a cable pull issue.)

It hasn't become clear yet whether more 10-speed groups with 4700's cable pull will be released, but I wouldn't wait for a bar-end version.