Maxie Masters's scanner
From Tardis Wiki, the free Doctor Who reference
P.R.O.B.E. technician and incognito alien Maxie Masters wore a scanner on her wrist.
It was able to detect that Varunastra was hugely powerful, with its readings being "off the charts". (WC: Varunastra [+]Loading...["Varunastra (webcast)"])