He's not selling it; it's listed as free.
It looks like a balance checker, but I don't actually know. A dev might know more, I'm sure you'll get a response from them soon.
This part:
"Add all your Pandacoin (PND) wallet addresses to see the total value". I don't know, putting your wallet address into an unknown app doesn't seem like a good idea. Who knows what this program is doing with those addresses behind the scenes? Why is it free? What is this guy's up side in putting this out there?
Putting your wallet address in something is fine. No one can do anything with your public address. Your public address can only be used to send pandacoin TO you.
The only way someone can steal from you is if they have your Private Key, which is different from your Wallet Address.
That said, the devs will probably know more than I.