Actually, they could go even lower-tech, and just hang out nearby and observe the Air Force One helicopter's route, pick a spot and wait in a van or apartment within blocks of the White House, and fire an RPG or surface-to-air missile at it as it flew over.
Or multiple suicide bombers could throw grenades from multiple positions at the president during a public appearance.
I can't bring a fruit cake into the US without Customs seizing it, so no idea how someone could bring an RPG into the country unless you can buy them at Walmart.
Senor Doctor - really? I didn't know that.
