What are some alternatives?
When comparing XE.com and Tweetbot, you can also consider the following products
Elk - The fastest way to convert currencies on mobile.
TweetDeck - TweetDeck is your personal browser for staying in touch with what’s happening now.
Unit Wolf - Unit conversions and calculator.
Twidere - Tired of seeing ads and promotions in your timeline, being disrupted by tweets from bots and people...
ConvertAll - A comprehensive unit conversion program.
Twitterrific - Twitterific is an app that offers several functions and fun features for your Twitter account.