Hi Dave,
I've had really positive experiences with tassomai. We ran it across a year group and were expanding to several years in several schools across our MAT.
Kids find it easy to access and responsive to them- it's continuous low stakes AfL- we used as hwk and in some form times/ etc.
Results improved, self marking, differentiated questions.
Informing parents too was helpful.
They're happy to work with you and act on feedback too.