No, GREP styles only apply formatting, they cannot insert characters. Use a regular find & change to do so.
(There is a thinking-outside-of-the-box solution. If you have access to a font creating utility, you can create a character 'h' with TM attached to it. Then you can use a GREP style to automatically apply this custom font to just the 'h' of 'Bluetooth'. See http://indesignsecrets.com/insert-a-special-character-with-grep-styles.php.)