I praised the TK-421 for a keyboard layout that made many keys easily accessible with only one or two taps. Although the MiniKey has a more compact keyboard, it also makes good use of space. Basically, each key has at least two options, with each option being accessible either directly or by tapping the Shift or Fn key. One tap on the Shift key before typing letters allows you to capitalize the first letter. The keyboard then reverts to lower case automatically. Tap the Shift key twice and you can type an entire word or sentence in capitals. This procedure also works with Shift and Fn when you want to type individual numbers and punctuation marks or a string of such characters.
In addition to Shift and Fn there is a Command Key. Tap this once and you can use the arrow keys to jump to the beginning or end of a document or line. If you select a word or text string using Shift and the arrow keys or by double-tapping the touch-screen, you can use Command + C and then Command + V to copy and paste. These key combinations are simple to use but redundant if you use the touch-screen method to select text because copy and paste are accessible with one additional tap on the screen. According to the MiniKey's instructions, you can also use Command + A to select all text. Either the instructions are unclear or I was being dim because every time I tried this key combination nothing happened.
Notwithstanding this minor issue, using the MiniKey with an iPhone is easy. The first thing to do is charge it with the included USB cable. Once it has power, you switch it on using a small slider above the keys. The On switch of the MiniKey is much better designed than that of the TK-421, which was barely operable. The MiniKey's switch also has three positions: Off, On and On with a backlight that illuminates the keys. The backlight is useful if you need to type in low light such as on an overnight flight or after the lights go out in a prison cell (well, why not?).
You pair the MiniKey with a phone by activating the latter's Bluetooth option from its Settings app. As with other Bluetooth devices, you will be prompted to enter a four-digit code. I found this to be a quick and reliable process with the MiniKey. It retained the code even when put into stand-by mode (which you do by sliding the keyboard back under the case). This often wasn't the case with the TK-421.