foobar one handed key map for twittering on iPhone.

keymap.c

#include QMK_KEYBOARD_H

#define _QWERTY 0
#define _PN 1

extern keymap_config_t keymap_config;

// tap dance
enum {
  KC_KG = 0,
  KC_SZ,
  KC_TD,
  KC_HB,
  KC_MP,
};

// Fillers to make layering more clear
#define _______ KC_TRNS
#define _ KC_TRNS
#define XXXXXXX KC_NO

qk_tap_dance_action_t tap_dance_actions[] = {
  [KC_KG]  = ACTION_TAP_DANCE_DOUBLE(KC_K, KC_G),
  [KC_SZ]  = ACTION_TAP_DANCE_DOUBLE(KC_S, KC_Z),
  [KC_TD]  = ACTION_TAP_DANCE_DOUBLE(KC_T, KC_D),
  [KC_HB]  = ACTION_TAP_DANCE_DOUBLE(KC_H, KC_B),
  [KC_MP]  = ACTION_TAP_DANCE_DOUBLE(KC_M, KC_P),
};

#define TD_KG TD(KC_KG)
#define TD_SZ TD(KC_SZ)
#define TD_TD TD(KC_TD)
#define TD_HB TD(KC_HB)
#define TD_MP TD(KC_MP)

const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
[_QWERTY] = LAYOUT_ortho_4x12(
   _, _, _, _, _, _, _, KC_N,   TD_TD,   TD_SZ,   TD_KG,   MO(_PN), \
   _, _, _, _, _, _, _, KC_W,   KC_R,    KC_Y,    TD_MP,   TD_HB, \
   _, _, _, _, _, _, _, KC_O,   KC_E,    KC_U,    KC_I,    KC_A,    \
   _, _, _, _, _, _, _, _______, _______, _______, _______, _______ \
),
[_PN] = LAYOUT_ortho_4x12(
   _, _, _, _, _, _, _, _______, KC_ENT,  KC_SPC,  KC_BSPC, _______, \
   _, _, _, _, _, _, _, _______, _______, _______, _______, _______, \
   _, _, _, _, _, _, _, KC_MINS, KC_DOT,  KC_COMM, KC_QUES, KC_EXLM, \
   _, _, _, _, _, _, _, _______, _______, _______, _______, _______ \
),

};

#undef _