The sonic suitcase was a device created by the Eighth Doctor during his century-long amnesic exile to Earth in the 1980s.
Even with his recollection of the sonic screwdriver lost with the rest of his memory, the Doctor retained enough residual knowledge to know how such a device could function. He attempted to recreate it in his spare time, but the limited technology of the time meant that the best he could accomplish was a device the size of a standard suitcase.
It was capable of holding objects within it to present the illusion of being a standard suitcase. The Doctor perfected the device between the early and mid-1980s, using it to open locked doors in a standard tower and even the door to the space shuttle Atlantis. The suitcase was eventually destroyed during the battle on the Supremacy. (PROSE: Father Time)