Article:
D&D 4th ed: High Tech weapons made easy.

In 4th edition, magic and technology are essentially the same thing. There is little difference between a rod that shoots fire, or a laser weapon that emits beams of radiant energy. Both require knowledge in Arcana to unlock their secrets (and decipher the instruction manual), both are a combination of keywords and damages appropriate to the level of the character. The main hurdle is that technological devices are not restricted by uses of the items per day, but again, this is an easy fix.
Technological items require power, the majority are designed to regenerate it slowly over time, and thus, you have one or two uses of it per day and then it needs to rest and restore itself for a while.
The only significant advantage of a technological weapon is a greater range capacity, and the fact that almost anyone can pick them up and unleash merry hell until the battery runs flat.

I've created a set of simple random roll tables in five easy steps, so that you can throw together a new technological weapon in a jiffy.

Step One: Type of Weapon.
Roll 1d20
1-2 : Ring.
3-4 : Ball.
5-6 : Rod.
7-8: Visor or Gauntlet.
9-10 : Pistol.
11-12 : Sub Machine Gun.
13-14 : Rifle.
15-16 : Staff or Lance.
17-18 : Bazooka.
19-20 : Portable Canon.

Step Two: Damage Type.
Roll 1d20
1-2 : Arcane
3-4 : Thunder
5-6 : Poison
7-8 : Force
9-10 : Acid
11-12 : Fire
13-14 : Cold
15-16 : Lightning
17-18 : Radiant
19 : Necrotic
20 : Psychic

Step Three: Special Features.