Why do we need tools at all? Well, if you are trying to become a better player, you need to learn. And there are a lot of staff on Play Market which might help us to get more wins!
StarCraft 2 Build Player
https://play.google.com/store/search?q=starcraft 2 build&c=apps
Really cool app which use Google text to speech API to tell you when and what to do during the match. Despite the fact that this tool has possibility to add new build orders, tool can't help you optimize your build orders - you need to specify when and what you would like to do.
Latest update - 28 august 2013.
SC2 Build Timer
This is also build player tool which can help you to master some builds. A number of supported build orders is low and UI to add new build orders is not user friendly but still tool can be handy while learning new builds.
Updated 4 december 2013.
This tool focused more on crafting build orders. It support cool UI with full in-game economic model emulation. You only need to choose your next step like get SCV or build Refinery and tool will determine closest possible point in time when you can build this item. It is perfect for optimizing your build orders.
After latest update which happened 8 april 2015 tool contains almost 80 build orders from ImbaBuilds.com and TeamLiquid.com which make it a good build order library.
Tool has both Free and Paid version. The only restriction of free version is that you allowed to use tool only for 1 faction and add-on (WOL, HOTS). LOTV support is also promised in next releases.
One disadvantage of this tool is that it does not have build Player functionality but this feature is also promised in next release.
Build Order Buddy
This is also build player tool and it has same advantages and disadvantages as other build players. UI to add new builds is not user friendly. It is hard to manage builds using this tool. This tool seems to be no longer supported since latest update was done 3 december 2011.
This is just a library of build orders. It has a lot of actual builds so might be very helpful.
Latest update 24 july 2014.