There are lots of resources (web, app, and even print) for increasing your vocabulary by one word per day. For this approach to be most effective, I would recommend adding your daily words to flashcard lists (perhaps arranged thematically, or b y radical) so that you can review regularly.
Several iOS developers maintain Chinese word-of-the-day apps. All links are to the iTunes App Store (prices as of post date).
First, Declan Software. Each includes pinyin (with tone numbers) and audio. You can also share your daily word by e-mail, Facebook, or Twitter.
Chinese Word of the Day – Declan Software. Free.
Chinese (Traditional) Word of the Day – Declan Software. Free.
Next up, Prometoys. This app actually gave me nine words when launched for the first time. For some reason the part of speech is a big icon and the hanzi very small. No pinyin or audio, but it does give example sentences. There’s no explicit mention of Transparent Language in the app, but the words seem to be pulled from their word-of-the-day feed.
Mandarin Word of the Day – Prometoys Limited. Free; ad-supported.
Then there are the seemingly identical apps from Ronald Bell. These only give pinyin (with tones) and English. You can move backward and forward through the inventory of words.
Mandarin Word of the Day – Ronald Bell. Free; ad-supported.
Mandarin Daily Word! – Ronald Bell. Free; ad-supported.
Chinese Word of the Day! (Mandarin) – Ronald Bell. I assume this one omits the ads, but I won’t pay to find out. $.99.