Test for SelectedItem in any slot

/testfor @a {SelectedItem:{id:minecraft:blaze_rod}}
/testfor @a {SelectedItem:{id:minecraft:tripwire_hook,tag:{display:{Name:"key"}}}}

/scoreboard players remove @a[score_display_min=1] display 1 {SelectedItem:{id:minecraft:blaze_rod}}

/scoreboard players add @a Snowball 1 {SelectedItem:{id:minecraft:snowball,tag:{display:{Name:"WhiteFire",Lore:[Creates Fireball When Thrown]}}}}

/testfor @p[r=10] {Inventory:[{id:"minecraft:emerald",Count:2b}]}