200 coins per app. I have no idea whether any of the 5 apps is any good, but the 1000 points can be put to good use. Equivalent to US$10.
Edit: to get or spend coins your device needs to be linked to Amazon US. You can do that in two steps:
1) In "Your Account" under "Address Book" add any US address (hotel, fictional).
2) Also in "Your Account" under under "Digital Management" go to "Manage Your Content and Devices" - from there you find "Country Settings" on the left, pick the US address
Thanks to Cardz for his tip below, I copy it here to make it easier to find:
If you haven't already with your 1000 credits buy GTA SA
It will cost you 700 credits but you will get a further 2000 credits
http://www.amazon.com/Grand-Theft-Auto-Andreas-Kindle/dp/B00…
It says gta is not compatible with your device on my nexus 5 , any workarounds ?