Paribus is described as 'Stores change their prices all the time. Paribus gets you money when prices drop. So if you buy something and it goes on sale later, Paribus automatically works to get you the price adjustment'. There are 2 alternatives to Paribus for iPhone, Online / Web-based and Android. The best alternative is Slice, which is free.
Slice lets you track your package shipments and deliveries automatically, by linking to your Yahoo or Gmail email inbox. It parses your email accounts, looking for receipts for your favorite merchants like Amazon, eBay, Groupon, Apple, Walmart, Newegg, Target, and Best Buy.
Earny gets you money back on almost every purchase you make. Stores promise that if the price of an item you purchased goes on sale within 14 days of your purchase, they will refund you the difference. Major credit card issuers guarantee the same policy for up to 90 days.