See item 6 in Using LINUX commands in App Inventor. Extension - #7 by TIMAI2
I find that satellite data NMEA sentences are remarkably accurate (using the ALS extension with an Android device). If corrupted data strings is a huge problem I suspect sampling from your Arduino maybe too fast and cutting off data; perhaps a slower sampling rate? Yes, most sentences contain a checksum you could compare with the data you read. I solved data quality by filtering out 'sentences' that I do not use. Perhaps you can limit what 'sentences' are read?