Not sure if your friend is talking about you behind your back? Well then perhaps he or she could use a great Seal of the United States with a bug in it, like, say the one the Soviet Union gave U.S. Ambassador Averell Harriman as a gift of friendship back in 1945:
Their definition of friendship was a little dysfunctional, though, because the gift contained a bug designed by famous Russian inventor Leon Theremin. The bug was hard to detect because it was extremely thin, gave off no signal and had no power supply.
There are plenty of other great gift ideas from history on this great Mental Floss article.