I have seen videos of people starting their motorcycle using an arduino and an android device
i know they use apps like appinventor to make the apps, but i dont know how to build one myself. Does any ody know? 
Try asking the people who made the videos you like.
Or Google.
This has been done and written up many times; it's a fairly popular project. Google will find you some writeups where people talk about how they did it; you should start with those.
...but don't forget to inform your insurance company.
Of course i will inform them! But i haven't found any good tutorials/info about it tried searching on youtube and google and when i ask the people who has done it says that they wont show how to 
well i better just dig a little more deeper