This application ensures that there will be equal numbers of interventions in any subgroup that is designated. There can be any number of observations, up to five interventions and five subgroups. The application does all the hard work of distributing subjects evenly across subgroup, with equal numbers allotted to each treatment arm.
Each subgroup has a different order of randomized allocations. Once the lists are generated in either .csv form or a format useable for ticking off entry to the trial, they can be emailed or sent to a local printer accessible from the iPhone
Professor Rand Wilcox of the University of Southern California (Author of "Introduction to Robust Estimation and Hypothesis Testing. A volume in Statistical Modeling and Decision Science") says: "Looks like a very convenient and useful tool."
The 5th edition of his book is due out around November 2021.
Commercial companies charge thousands of dollars to randomize data. (For example, see https://randomize.net/#pricing) Of course, they may offer many additional features, but why pay this amount for such a simple task when using this application?