I've been researching your question on and off since last night. The only information I can find about houdini and walls is his ability to walk through them rather than see through them.
I did find an article where Houdini tested a man who claimed this ability and proved him to be lying.http://www.findarticles.com/p/articles/mi_m2843/is_3_29/ai_n13676394
Sorry I couldn't be more help.
A 1959 biography of Houdini bore the subtitle The Man Who Walked Through Walls. (Henning 1977) - see link below:
It was reported that Houdini died without revealing his secrets of success - but later found that 4 friends knew about his secrets.
Houdini in The New York Times, Says Four Know Houdini's Secrets
Speculations of Houdini discovering the 4th dimension.
Amazon.com: Dear Professor Einstein: Albert Einstein's Letters to and from Children: Explore similar items
(Higher dimensional people have the ability to "walk through walls" -- 4th/5th dimensional and higher).
Hyperspace: A Scientific Odyssey through the 10th Dimension
The book below may offer you some information:
WONDER-WORKERS! How They Perform the Impossibleby Joe Nickellfor ages 9-14(Prometheus Books, October 1991, $11.95, ISBN 0-87975-688-8)review by Cindy BartorilloNickell investigates the apparently impossible accomplishments of ten famous wonder-workers: Ivan Chabert (who was impervious to heat), Robert-Houdin (one of the greatest magicians of all time), Daniel Home (who could float through the air), Lulu Hurst (whose body was a powerful magnet), Evangeline Adams (who could foretell the future),Harry Houdini (who could, among many other talents, walk through walls), Joaquin Argamasilla (whose x-ray eyes could see through metal), Joseph Dunninger (who could read minds), Edgar Cayce (who could diagnose illnesses while asleep), and Peter Hurkos (a psychic detective).
Houdini had an "open mind" and believed that there was a world beyond "human" -- using power within and above/tapped into it!
His favorite quote:"my brain is the key that sets me free"
HOUDINI: Interesting Houdini Facts Houdini Museum Scranton Pocono region. Houdini magic museum, Houdini magic show, magic, Sc...
Hope this helps.
Peace, Love & Happiness,
The Mystic Wave
To better assist you, what makes you believe he had a "gadget" - where did you hear this information?
Please let me know...
Also, please note that I responded to your question - see above.
Thank you for responding and sharing more information, and for letting me know that you did see my response.
Now I am confused - are you wanting to find out the "gadget" or "thing" for "seeing through walls" or "walking through walls"...you originally stated "walking through walls".
Please let me know.
My sincere apologies, I erred.
The only thing that I have found that comes close to any type gadget of seeing through walls would be an "x-ray render view".
If this is not what you are looking for, I do apologize. Of course, the listing of information I provided (specifically the book titles) may just have such reference in which to answer your question.
My best to you.