Trade42 is a MTG card trading assistant which mirrors many of the features available at the online Trade Helper page, other than loading the images for each card.
Two lists of cards (blue and green) automatically calculate the total value of the cards in each list.
Cards can be toggled on and off to count towards the total, moved between lists, and have their prices edited if you don't like the default price.
The prices fetched from ark42.com are always up to date automatically.
Search for cards on the main screen. When the Search button is pressed, each word will be matched against the list of known cards online.
For example, you could just type "lili vei" to match "Liliana of the Veil" easily.
Each search will result in two prompts, to select the exact card name and printing you wish to add. Then the card will be added to the selected color trade list.
If you add cards to the wrong list, don't worry, you can always move them between the lists later.
Pressing the card rows in the trade lists will toggle them between colored and greyed out. When they are greyed out, the card's value no longer counts towards the total listed at the top of that list.
Pressing and holding for a brief momment on a card row will bring up an option menu for that card.
From this menu, you can adjust the card's price, add additional copies of that card, move the card to the opposite list, or remove the card from the list altogether.
When the trade is complete, remember there is a clear trade option in the menu choices for the app.
Download free APK at http://ark42.com/mtg/trade42/