I'd be careful with package tracking. While I don't know if that particular app resell your purchase data. That one is paid, so they may not need to right now,

I'd be careful with package tracking. While I don't know if that particular app resell your purchase data. That one is paid, so they may not need to right now, but they may change that in the future. I know many other similar (Slice, Unroll.me, etc.) products do. It's an easy, high ROI monetization strategy.