This cross laser could be useful for both big and small projects. No need to look for a power outlet, since it runs on batteries. Just get at it!
From Amazon
Einhell TC-LL 2 Cross Line Laser Level With Working Range of 8m | Digital Spirit Level, Horizontal And / Or Vertical Laser Line, Self-Levelling, LED Warning | Includes Storage Case
Conrad Electronic
Einhell TC-LL 2 Cross line laser Incl. bag Range (max.): 8 m
Robert Dyas
Einhell TC-LL 2 Cross Laser Level with Storage Bag