Every one of the 50 states and the District of Columbia have statutes that provide that a will must be in writing. Most of them say it must be signed "at the end", and many of them require two or three witnesses.
Nevada has a ground-breaking statute that permits digital wills, but apparently the software required to meet the requirements of the law has not been developed. The law requires that the digital will must be just as verifiable as a will on paper. There must only be one authoritative copy (similar to only one paper original), any copy must be clearly a copy, and the signature on the will must make it uniquely an act of the testator. The electronic will must also include an "authentication characteristic" such as a fingerprint or retinal scan to prove it was the act of the testator and only the testator. Apparently the "one authoritative copy" requirement has been the biggest challenge to software developers given the ability of the computer to make copies.
Written doesn't necessarily mean on paper. A Canadian farmer got trapped under his tractor and managed to scratch out a short will on the fender, leaving all to his wife. A will written on a plaster wall leaving all to a man's fiancee was cut out and offered for probate, but it looked more like a power of attorney than a will. A case in Montana was similar and the will was refused at probate. A will written on the bottom of a drawer leaving all property to a man's son was accepted.
An Ohio judge recently approved a will written on a Samsung Galaxy tablet. The testator was in a hospital in need of a transfusion which he refused on religious grounds. The will was written with a stylus on the digital tablet since there was no paper handy. The will was "signed" by the testator and witnesses and later printed out and submitted for probate. The judge made mention of the Nevada law in upholding the will and called for the Ohio state legislature to help out by enacting legislation.
Joseph M. Mentrek in his article in the Probate Law Journal of Ohio says "... paper wills have a big advantage over electronic wills. There's a common misconception that the impermanent nature of paper makes digital storage superior. But in fact the opposite is true. Paper can last hundreds of years, while CDROMs, hard drives and other digital storage media tend to degrade much more quickly. In addition, because of rapid advancements in technology and a lack of standardization, even if an electronic document were to remain intact, there is no guarantee that the hardware and software needed to read it will be available in the future."
Sometimes a video of a will execution is made, not to be a substitute for a written will, but to prove that all the requirements of a will execution were accomplished. The video is intended to provide evidence that the testator signed the will by himself, that the witnesses were within line of sight of the Will being signed, and that the witnesses signed and the notary public authenticated the identity of the parties all at the same sitting. But the tape or disc is not a will.
One case in Colorado involved a videotaped recitation of a will by the testator. The videotape was then put in an envelope and sealed and the testator signed the sealed envelope. Many thought that the sealing and signing of the envelope should legitimize the tape as a valid will, but the court ruled otherwise, relying on the universal rule that a will must be in writing.
As legal history goes, people haven't been able to make wills for all that long. Before the 1500's in England no wills were permitted. Sometimes people made lifetime transfers of real property trying to get around the problem. But the Statute of Uses in 1535 put an end to the practice of transferring land to a beneficiary during life but retaining the use of it until death. In 1540, the Statute of Wills enabled disgruntled land owners to transfer land in a will but required that a will transferring real estate be in writing. It allowed oral wills for personal property.
People expressed their wishes regarding passing on what they own verbally, often on their death bed. That, of course, led to lies and shenanigans which the law slowly but surely addressed.
After a case in 1676 where a young wife of an elderly rich man claimed in court that he made an oral will leaving everything to her despite a previous written will leaving everything to charities. A string of nine witness attested (falsely) to the young wife's claim. The very next year, the Statute of Frauds declared that oral wills would always be trumped by written wills, even if the oral will came later. The Wills Act of 1837 stated that all wills must be written and signed by the testator and witnessed by two witnesses, neither of whom could be a beneficiary of the estate.
Wills are touchy subjects and supremely important to the beneficiaries, not to mention the testator. People are slow to accept new technology. Maybe in another ten years technology will have advanced to make digital wills possible. But how long will it take them to be accepted?