Looking for a calories counting app with a specific purpose

I'd like to be able to have a calorie budget that counts down as I log foods throughout the day, so I can motivate myself to use my calories more wisely.

I've been using a Fitbit Alta HR for the last couple of days, and the general burnt calories doesn't help much AFAIK.

Also, since I'm on topic: any app you'd suggest to pair with the fitbit? Aside from the Fitbit app itself?