It is quite common to find tools that report on statistics per variant/marker, given a vcf file, but does anyone know of a tool that can report on stats per sample?

More specifically, I am looking for a tool that can tell me the proportion of variants/markers that are heterozygous (1/0 or 0/1) for each SAMPLE, given a vcf file.
[RTG Tools][1] includes a `vcfstats` command that outputs basic statistics for every sample (or you can request specific samples). e.g. on a small simulated vcf:

```
$ rtg vcfstats family.vcf.gz

Location                     : family.vcf.gz
Failed Filters               : 0
Passed Filters               : 144

Sample Name: sm_mom
SNPs                         : 91
MNPs                         : 1
Insertions                   : 5
Deletions                    : 2
Indels                       : 0
Same as reference            : 1
Missing Genotype             : 44
SNP Transitions/Transversions: 1.74 (73/42)
Total Het/Hom ratio          : 2.96 (74/25)
SNP Het/Hom ratio            : 2.79 (67/24)
MNP Het/Hom ratio            : - (1/0)
Insertion Het/Hom ratio      : 4.00 (4/1)
Deletion Het/Hom ratio       : - (2/0)
Indel Het/Hom ratio          : - (0/0)
Insertion/Deletion ratio     : 2.50 (5/2)
Indel/SNP+MNP ratio          : 0.08 (7/92)

Sample Name: sm_dad
SNPs                         : 73
MNPs                         : 2
Insertions                   : 2
Deletions                    : 3
Indels                       : 0
Same as reference            : 1
Missing Genotype             : 63
SNP Transitions/Transversions: 1.87 (58/31)
Total Haploid                : 19
Haploid SNPs                 : 17
Haploid MNPs                 : 0
Haploid Insertions           : 1
Haploid Deletions            : 1
Haploid Indels               : 0
Total Het/Hom ratio          : 2.59 (44/17)
SNP Het/Hom ratio            : 2.50 (40/16)
MNP Het/Hom ratio            : 1.00 (1/1)
Insertion Het/Hom ratio      : - (1/0)
Deletion Het/Hom ratio       : - (2/0)
Indel Het/Hom ratio          : - (0/0)
Insertion/Deletion ratio     : 0.67 (2/3)
Indel/SNP+MNP ratio          : 0.07 (5/75)

[...]
```

 [1]: http://realtimegenomics.com/products/rtg-tools/