Here's a link to a few versions of it, followed by my personal review:
Slice helps you budget! It does this in a variety of ways:
1- It automatically keeps a history of purchases made (by pulling receipts, shipping statements, order verifications, etc from your email.)
a- It tracks total spending, date of each purchase, and item specifications (even MFR and shipping phone numbers (UPS,USPS, FedEX, etc).
b- It actively tracks shipping, removing the need to check UPS or other websites. Gives a projected delivery date, as well as saves the actual delivery date in case you ever need to check when you received an item.
2- It helps make saving money easier (especially for computer building IMO) by notifying you of sales.
a- You can set custom parameters for price change on items you have previously bought to be notified of price drops in the future. If you buy a lot of something (thermal paste, fan filters, etc) this is a very handy feature!
b- I've been told (but haven't tested out/seen myself) that it can be set to do the same for items you have not purchased. Useful if you're (ie) waiting for a set of RAM to go on sale, but not wanting to check newegg every single day.
It tracks every purchase to the last detail. Occasionally one or two details is missing, but it's usually the warranty termination date (yes, it tracks those too!) that doesn't load for me. This helps you to keep a comprehensive list of everything you've bought, where you bought it, how much it was, when it was shipped, who to call for shipping errors and RMAs: And much more.
And the best part:
All you have to do is hook it up to your email. No extra steps, no complicated configuration, It's that easy to get everything set-up!
Personally I've been recommending this app like a new drug, and I don't usually recommend anything. So take that tidbit and go check it out!
--I've only used Slice for Android, and the accompanying desktop site. I cannot personally vouch for the iPhone version.