I've recently published an Android app that is intended for use as a board game currency (think Monopoly etc.).
Because it is intended for multiple types of game, and because even within Monopoly the order of magnitude of transaction values can vary, I allow users to quickly choose multipliers of 10^6 and 10^3, to save typing the extra zeros.
One bit of feedback I've had from several users is that the way these options are presented is confusing. It has lead users to mistakenly send transfers of e.g. £2 when they meant to send £2M -- because they thought the 10^6 multiplier was selected when it wasn't.
I want to improve this bit of the UI but I have limited screen space to work with and am unsure what would be best.
The screenshot below is how it currently is. I show the current multiplier as either an M, K, or nothing at all to the right of the value field ("£2.4M" in the screenshot). The radio buttons to the far right are how it is changed. I should point out that unfortunately radio buttons in Android only allow the label to be shown to the right of the button itself.
How can I make the multiplier selection clearer without cluttering the layout?